- 


* 


LIBRARY 


'V 

UN 


IVERSITY   OF  CALIFORNIA 

Received 
Accessions  No.^Z'fX'P       Shelf  No 


STEAM  USING; 


OR 


Steam  Engine  Practice, 


CHAS.  A.  SMITH,  0.  E., 

Professor  of  Civil  and  Mechanical  Engineering  at  Washington   University,  St. 

Louis,  Mo.;  Member  of  the  American  Society  of  Civil  Engineers,  the 

Engineers'  Club  of  St.  Louis,  and  Associate  Member  of  the 

American  Association  of  Railway  Master  Mechanics. 


CHICAGO: 
THE  AMERICAN  ENGINEER,  182-184  DEARBORN  STREET. 

1885. 


Entered  according  to  act  of  Congress,  in  the  year  1884,  by  * 

PROPRIETORS  OP  THE  AMERICAN  ENGINEER, 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C. 
^ 


PRESS  OK 

JOHN  W.  WESTON, 
CHICAGO,  ILL. 


PUBLISHERS'   PREFACE. 


It  is  believed  that  some  knowledge  of  the  circumstances  attending  the 
publication  of  this  work,  'STEAM  USING,  "as  well  as  its  companion  volume, 
"STEAM  MAKING,"  will  be  of  interest  to  the  reader. 

The  lamented  author,  Prof.  Chas.  A.  Smith,  had  arranged  with  The 
American  Engineer  for  the  publication  of  the  two  works.  While  the  first, 
"STEAM  MAKING, "  was  going  through  the  columns  of  the  Engineer,  Pro- 
lessor  Smith  died,  early  in  1884,  leaving  also  to  the  care  of  the  Engineer 
the  recently  completed  manuscript  of  "STEAM  USING." 

To  all  who  are  familiar  with  the  circumstances  under  which  the  books 
were  written — the  author  suffering  from  a  mortal  illness  and  struggling 
against  death  to  thus  round  out  his  life  work,  only  giving  up  to  die  on 
their  completion — will  appreciate  and  value  the  more  highly  the  broad 
and  active  experience  thus  crystallized. 

To  Mr.  John  W.  Weston,  so  long  connected  with  this  journal,  and 
personally  familiar  with  the>author  and  his  writings,  has  been  delegated 
the  pleasant  duty  of  conducting  these  works  through  the  various  stages 
of  bookmaking,  with  the  result  now  presented.  The  task  has  not  been 
without  its  difficulties,  the  most  serious,  perhaps,  being  the  loss  of  the 
invaluable  assistance  of  their  author  in  the  work  of  revision  of  matter 
and  proof. 

As  the  author  died  without  leaving  a  preface  to  his  second  volume,  we 
desire  to  acknowledge  for  him  the  aid  which  he  received  from  various  en- 
gine builders  and  professional  men  throughout  the  country,  which  the 
following  pages  will  disclose 

It  has  been  the  aim,  as  far  as  possible,  to  preserve  the  exact  style  of 
the  author,  and  it  is  believed  that  the  facts  and  features  presented  in  both 
books,  the  heirlooms  of  an  admirable  man,  acknowledged  to  be  profound 
and  exact  in  his  particular  lines  of  work,  will  be  held  to  cover  whatever 
defects  of  minor  importance  may  be  encountered. 

THE  AMERICAN  ENGINEER. 

CHICAGO,  MARCH  1,  1885. 


s& 


SKETCH  OF  THE  LIFE  AND  CHARACTER 
OF  THE  AUTHOR. 


Charles  A.  Smith  was  born  in  St.  Louis,  October  1,  1846.  His  parents 
were  both  Massachusetts  people  who  had  been  still  further  west.  From 
both  father  and  mother  he  inherited  the  instincts  of  a  sailor,  and  the 
blood  of  several  generations  of  ship-masters  coursed  through  his  veins. 
Though  he  never  became  a  sailor,  he  always  showed  a  sailor's  fondness  for 
"fixing  things,"  for  using  his  hands,  for  actual  construction. 

While  he  was  still  an  infant,  his  mother  died  of  cholera  in  St.  Louis, 
and  he  was  placed  in  the  care  of  his  father's  sister,  in  Newburyport,  Mass. 
This  kind  aunt  was  his  mother,  and  her  house  was  his  home  till  he  had  a 
home  of  his  own.  His  mode  of  life  was  simple  and  plain,  but  young 
Smith  made  warm  friends  and  his  boyhood  was  happy. 

I  first  met  him  in  1860,  when  I  became  principal  of  the  Boys'  High 
School,  of  Newburyport.  He  was  then  fourteen  years  old  and  a  member 
of  the  second  class.  He  was  a  pleasant  little  fellow  with  a  frank,  earnest 
look,  and  a  forehead  which  suggested,  brains.  When  the  school  gave 
expression  to  its  loyalty  to  the  Union  by  the  erection  of  a  liberty  pole  and 
publicly  celebrated  a  flag-raising,  young  Smith  was  selected  by  his  school- 
mates to  mount  the  platform  and  haul  home  the  stars  and  stripes. 

The  school  had  a  very  good  theodolite,  and  when  we  came  to  Loomis' 
Surveying,  a  great  enthusiasm  for  field  work  was  developed,  and  young 
Smith  was  never  so  happy  as  when  on  a  surveying  party.  He  took  the 
English  course  and  graduated  in  1862.  The  next  spring  he  went  into  the 
office  of  J.  B.  Henck,  civil  engineer,  in  Boston.  At  that  time  he  probably 
had  no  idea  of  going  to  an  engineering  school.  In  1864  he  was  leveller  on 
the  Boston,  Hartford  &  Erie  Railway.  In  1865  he  became  chief  assistant 
in  the  City  Engineer's  office,  Springfield,  Mass.  By  this  time  he  saw 
clearly  that  an  engineer  requires  a  training  far  beyond  a  high  school 
education,  and  he  resolved  to  enter  the  Massachusetts  Institute  of  Tech- 
nology, then  first  opened  He  had  been  reading  ahead  somewhat,  with 
occasional  help  from  me,  so  that  he  entered  what  was  organized  as  a 
sophomore  class.  He  lived  again  in  Newburyport  and  went  eighty  miles 
daily  on  his  way  to  and  from  the  Institute.  President  Rogers  was  his 
teacher  in  physics,  Professor  Runkle  in  mathematics  and  applied  mechan- 
ics, and  Professor  Henck  in  civil  engineering. 

He  graduated  in  the  pioneer  class  in  1868.  I  never  quite  understood 
how  he  managed  to  meet  the  cost  of  his  course  at  the  Institute.  To  be 
sure  he  had  carefully  saved  the  earnings  of  three  years,  and  he  secured 


VI.  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


for  his  vacations  most  excellent  employment  under  the  celebrated  hy. 
draulic  engineer,  J.  B.  Francis,  at  Lowell,  Mass.  He  there  assisted  in 
determining  the  flow  of  water  in  pipes,  over  wiers,  the  efficiency  of  tur- 
bines, etc.  I  left  Massachusetts  for  St.  Louis  in  1865,  so  I  did  not  follow 
closely  his  career  as  a  student. 

After  a  year  as  engineer  on  the  Union  Pacific  Railway  in  Utah,  he 
returned,  on  the  completion  of  the  road,  to  Boston  and  went  into  partner- 
ship with  Professor  J.  B.  Henck,  as  civil  engineers.  While  there  associated 
with  Professor  Henck,  he  took  charge  of  a  part  of  the  Blue  Ridge  Rail- 
way  of  North  Carolina,  as  division  engineer. 

At  that  time,  in  1870,  the  steady  development  of  the  Polytechnic 
School  of  Washington  University  made  it  necessary  to  appoint  an  instruc- 
tor of  civil  engineering.  I  took  pleasure  in  recommending  young  Smith 
for  the  position,  and  he  was  appointed.  For  the  first  year  he  made  his 
home  in  my  family,  and  as  a  preparation  for  the  work  of  the  class  room  he 
read  with  me  Eankine's  Civil  Engineering  entire. 

After  a  brief  experience  as  instructor,  Mr.  Smith  was  appointed  pro- 
fessor to  the  chair  of  civil  and  mechanical  engineering,  which  was  subse- 
quently named  in  honor  of  William  Palm.  This  chair  Professor  Smith 
held  till  June,  1883,  when  compelled  by  his  last  illness  to  resign. 

Though  devoted  at  all  times  to  the  work  of  his  professorship,  Profes- 
sor Smith  found  time  to  mingle  in  matters  of  practical  engineering.  For 
five  years  he  was  consulting  engineer  of  the  Iron  Mountain  Railway, 
among  other  things  designing  the  DeSoto  shops,  and  building  a  new  pier 
in  the  Black  river.  In  a  similar  way  he  was  associated  with  Messrs, 
Shickle,  Harrison  &  Co.,  designing  the  arched  ribs  of  the  roof  over  the 
Chamber  of  Commerce,  and  the  iron  trestles  of  the  Bessemer  Iron  Works. 
Professor  Smith  was  engaged  as  consulting  engineer  for  the  construction 
of  the  water  works  of  Hannibal,  of  St.  Charles,  in  Missouri,  and  of  Ames- 
bury,  Massachusetts.  His  last  professional  duties  were  in  connection  with 
the  last  named.  The  pumping  works  at  Richmond,  Va.,  were  designed  by 
him,  his  plans  being  entered  in  competition  and  receiving  the  first  prize. 
In  1879  he  spent  his  summer  vacation  as  resident  engineer  of  the  Balti- 
more Bridge  Company,  building  piers  in  the  Mississippi  river  just  below 
Minneapolis. 

Without  attempting  to  give  a  full  list  of  the  professional  enterprizes 
of  Professor  Smith,  I  have  said  enough  to  show  how  tireless  a  worker  he 
was,  and  how  closely  he  studied  the  practical  details  of  engineering.  But 
it  was  in  connection  with  the  St.  Louis  Engineers'  Club  that  his  devo- 
tion and  enthusiasm  were  most  fully  shown.  He  was  an  active  mem- 
ber for  twelve  years,  and  the  secretary  for  nine  or  ten  years.  The  club 
has  not  always  been  as  flourishing  as  it  is  now.  It  has  had  its  seasons  of 
depression  when  only  the  zeal  and  the  courage  of  Secretary  Smith  seemed 
to  hold  it  together.  Nothing  but  the  direst  necessity  compelled  him  to 
yield  at  last. 

The  fatal  malady,  which  in  the  shape  of  a  cancerous  tumor,  brought 
his  life  to  an  untimely  close  on  the  2nd  of  February,  1884,  was  born,  as  he 


LIFE  AND  CHARACTER  OF  THE  AUTHOR.  VII. 


thought,  of  hard  work,  of  exposure,  and  of  physical  neglect.    He  could 
scarcely  stop  to  eat  or  sleep;  it  was  work  first  and  comfort  last. 

Nothing  in  Professor  Smith's  life  was  more  heroic  than  the  way  he 
battled  for  two  years  against  an  impending  fate.  When  too  weak  to  stand 
before  his  class,  he  taught  reclining  upon  a  lounge.  One  of  his  last 
pupils  speaks  in  a  notice  of  his  beloved  professor  of  "the  days  of  suffer- 
ing spent  in  his  study  in  the  University,  when  we  gathered  round  him 
as  he  lay  on  the  lounge,  unable  to  stand,  and  listened  to  his  exposition 
of  'Economic  Location,'  taking  as  a  basis  the  work  of  his  friend,  Arthur 
Wellington." 

In  January,  1883,  he  was  forced  to  give  up  his  class  work  altogether, 
and  to  keep  his  room.  Still  he  was  not  idle.  Lying  on  the  bed,  or  reclin- 
ing in  an  easy  chair,  he  was  hard  at  work  upon  his  two  books  on  "Steam 
Making"  and  "Steam  Using,"  which  are  just  now  being  issued  by  the 
American  Engineer,  in  Chicago.  The  first  was  finished  by  the  end  of 
1882,  and  arrangements  were  made  for  its  publication,  but  the  prospect 
for  the  second  book  was  gloomy  enough.  Nevertheless,  he  worked 
at  it  with  a  terrible  earnestness  which  no  unfavorable  symptom  could 
diminish.  Nay,  though  clinging  to  the  faintest  glimmer  of  hope  of 
returning  health,  he  toiled  at  his  book  with  the  resolute  air  of  one  who 
was  fully  conscious  that  his  days  were  numbered,  and  that  the  book  must 
speedily  be  finished.  In  spite  of  pain  and  the  dark  shadow  of  the  inevit- 
able, his  mind  seemed  clear  and  his  hand  steady.  In  the  spring  of  '83 
he  moved  back  to  Newburyport,  Mass.,  to  be  near  his  physician  and  his 
family  friends.  There  in  a  quaint  old  house,  in  a  quiet  neighborhood  of 
that  quiet  town,  he  finished  his  book,  laying  down  his  pen  and  the  burden 
of  life  at  the  same  time.  The  readers  of  "Steam  Using"  may  be  glad  to 
know  that  the  author's  very  life's  blood  went  into  that  book;  that  it  was 
the  last,  the  most  perfect  fruit  of  a  very  active  and  noble  life. 

Professor  Smith  is  a  good  example  of  a  poor  boy  who  made  his  own 
way;  who  fought  his  own  battles;  who  earned  and  honored  every  position 
he  took.  He  was  always  a  student.  Some  of  you  will  remember  with 
what  enthusiasm  he  studied  quarternions  and  thermodynamics;  with 
what  zeal  and  success  he  read  all  that  he  could  get  on  graphical  statics, 
and  how  many  important  additions  he  suggested.  The  records  of  the 
St.  Louis  Club  probably  will  show  that  Professor  Smith  has  presented 
more  papers  than  any  other  member,  past  or  present. 

As  an  engineer,  Professor  Smith  was  bold  and  trustworthy.  His  confi- 
dence was  based  upon  sound  theory  and  careful  practice.  He  was  skillful 
in  preparing  estimates  and  was  always  well  informed  both  as  regards  the 
latest  improvements  in  engineering,  and  the  best  methods  of  working  the 
materials  of  construction. 

These  accomplishments  added  greatly  to  his  value  as  an  instructor  of 
young  engineers.  His  students  were  brought  veiy  close  to  engineering 
work.  Though  well  read  in  theory,  he  loved  to  dwell  on  the  details  of 
practice.  He  never  lost  an  opportunity  to  learn  a  new  process,  or  to  study 
a  new  machine.  He  used  to  tell  how,  while  resident  engineer  on  a  road  in 


VIII.  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 

New  England,  lie  tried  his  hand  on  the  engine  of  the  construction  train 
till  he  was  able  to  "stoke"  and  to  "drive." 

Professor  Smith  left  a  wife  and  three  children.  During  her  husband's 
long  and  discouraging  sickness,  Mrs.  Smith  was  better  than  a  faithful 
nurse:  she  brought  aid  to  his  self-imposed  labor,  and  hope  and  cheer  to 
his  fainting  spirit.  So  well  did  she  understand  the  nature  of  his  work 
and  his  needs,  and  so  helpful  was  the  assistance  she  brought,  that  it  is  not 
too  much  to  say  that  without  her  positive  cooperation  and  encouragement 
the  two  books  which  he  leaves  behind  would  never  have  been  finished. 

I  will  not  speak  of  personal  losses.  I  prefer  to  feel  that  we  all  had 
much  to  be  thankful  for  in  Professor  Smith,  and  the  nearest  had  the  most. 
Though  dying  in  his  thirty- eighth  year,  Professor  Smith's  memory  may 
well  be  preserved.  The  world  is  certainly  the  better  for  his  having 
lived  in  it. 

C.  M.  WOODWAKD, 

Dean  Polytechnic  School, 
Washington  University,  St.  Louis,  Mo. 

ST.  Louis,  December,  7,  1884. 


OOINTTIEiLTTS. 


CHAPTER  I. 

PAGE. 
ON  THE  NATURE  OF  HEAT  AND  THE  PROPERTIES  OF  STEAM: — 

Heat— Thermodynamics—Ratios  of  Volume  to  Pressure :  Regnault's  Ratios— 
The  Carnot  Engine — Making  steam — Measurement  of  Heat  Expended 
—Table :  The  Properties  of  Saturated  Steam— Examples  in  Calculation 
of  Heat  Expended,  Etc.— Table:  Factors  of  Evaporation— Its  Use- 
Table:  Expansion  and  Density  of  Pure  Water— Entrained  Water  and 
its  Measurement...  1—14 


CHAPTER   II. 


ON  VALVE  GEAR: — 


Action  of  the  Valve — Position  of  Valve  with  Regard  to  its  Eccentric,  Lap 
and  Lead— Valve  Diagrams  and  their  Application— Adjustable  Eccen- 
trics—The Link  and  Problems  Connected  Therewith— Gooch's  Link- 
Motion—Allan's  Link-Motion— The  Walschaert  Link-Motion-Mar- 
shall's  Valve  Gear— Brown's  Valve  Gear— Kirk's  Valve  Gear— Joy's 
Valve  Gear— Porter-Allen  Link  Motion— Herr  Kaiser's  Gear— The 
Meyer  Valve— Cut-off  and  Problems  Connected  Therewith— Ordinary 
Slide  Valves— Piston  Valves— Poppet  Valves— Double  Valve— Trick's 
Valve,  Etc 15—  56 


CHAPTER   III. 


THE  QUANTITY  OF  STEAM  WHICH  MIGHT  BE,  AND  WHICH  is  USED: — 

Horse-Power,  Indicated  Horse- Power,  Effective  Horse-Power,  Net  Horse- 
Power—Examples—Curve  of  Expansion  and  its  Properties— Data  fur- 
nished by  Experiment— Tables  of  Engine  Trials— Analyses  of  Results 
of  Practical  Tests— Internal  Radiation— Analysis  of  Experiments  Show- 
ing Effect  of  Internal  Radiation,  etc.— Tables 57- 


X.  CONTENTS. 


CHAP  TEE    IV. 

PAGE. 

ON  THE  INDICATOR,   THE  INDICATOR  DIAGRAM  AND  THE   DIFFER- 
ENT CLASSES  OF   ENGINES:— 

The  Construction  and  Use  of  the  Indicator— Other  Devices— The  Earlier 
Forms  of  Engines— Single  Acting  Engines:  The  Westinghouse,  The 
Brotherhood,  and  the  Colt  Disc  Engine — The  Indicator  Diagram  and  the 
Effects  of  Internal  Radiation,  etc.,  from  Actual  Experiments — Com- 
pounding and  Indicator  Diagrams  in  Connection  Therewith— Clearance 
—Forms  of  Compound  Engines— Progress  in  Marine  Engine  Perform- 
ances—Consumption of  Fuel— The  Value  of  Jacketting  and  Compound- 
ing—Poppet Valve  Eiver  Engines  and  Diagrams— High  Service  Pumping 
Engine,  St.  Louis  Water  Works— Indicator  Diagram  from  Lawrence, 
Mass.,  Pumping  Engine — Diagrams  from  Engines  of  Ocean  Steamers 
"Arizona"  and  "Aberdeen" — Engines  of  Mississippi  River  Steamer  "Mon- 
tana"— Engines  of  U.  S.  Lighthouse  Steamer  "Manzanita" — Triple  Ex- 
pansion Engines  of  S.  S.  "Aberdeen"— Compound  Engines  of  S.  S. 
"Grecian"— Three  Cylinder  Compound  Engines  of  S.  S.  "Parisian"— 
Automatic  Expansion  and  Governors— The  Wheelock  Engine— The 
Porter- Allen  Engine— The  Rider  Automatic  Expansion  Gear— Various 
Forms  of  Expansion  Slides  and  Valve  Gears — The  Cummer  Engine 
Governor — The  Armington  &  Simms  Engine— Engine  of  the  Steam 
Yacht  "Leila"— The  Locomotive— The  Buckeye  Automatic  Cut-off  En- 
gine—The  Reynolds'  Corliss  Engine— The  Lambertville,  N.  J.,  Auto- 
matic Cut-off  Engine— The  Porter-Allen  Engine 87—187 


CHAPTEK    V. 

THE  EXPERIMENTS  OF  HIRN  AND  HALLAUER: — 

Report  on  a  Memoir  Upon  Steam  Engines— Experiments  with  a  Steam  En- 
gine—Experimental Study  Comparing  the  Influence  of  Expansion  in 
Simple  and  Compound  Engines 188—285 

CHAPTEK    VI. 
STEAM  HEATING: — 

The  Theory  of  Steam  Heating— Various  systems  in  use  in  the  United  States 
—Description  of  Apparatus  and  Experiments  Used  by  the  Author- 
Project  for  Heating  a  Cotton  Mill. . .  . .  286—298 


STEA.M 

OR 

STEAM     ENGINE     PRACTICE. 


CHAPTER      I. 

ON  THE  NATURE  OF  HEAT  AND  THE  PROPERTIES  OF  STEAM. 

By  the  term  heat  we  understand  that  property  of  bodies  by  which  they 
grow  hot,  and  give  the  sensation  with  which  we  are  all  familiar. 

Heat  is  produced  in  three  ways: 

By  chemical  action,  A. 

By  mechanical  action,  B. 

By  electrical  action,  C. 

A. — When  certain  chemical  elements  or  compounds  are  combined  under 
certain  circumstances,  the  result  is  a  union  accompanied  by  an  increase  of 
temperature  and  the  development  of  heat;  as  for  example,  carbon  or  hydro- 
gen combining  with  oxygen;  sulphuric  acid,  or  quick  lime,  with  water. 

B. — By  the  mechanical  work  of  friction  or  percussion:  Examples  of 
this  are  continually  before  us. 

C. — By  the  passage  of  an  electric  current  in  a  conductor, — as  in  wires  of 
too  great  resistance;  or  the  electric  arc. 

The  pf6perty  of  heat  is  thought  by  some  to  consist  of  a  kind  of  motion 
or  vibration  of  the  molecules  of  which  bodies  are  supposed  to  consist; — for 
solid  and  liquid  bodies  in  vibration,  and  for  gaseous  bodies  in  the  real  mo- 
tion of  the  molecules.  With  the  arguments,  pro.  or  con.,  concerning  this 
hypothesis  we  have  little  to  do  further  than  to  state  that,  its  truth  appears 
very  probable,  and  in  such  event  the  production  of  heat  by  chemical  com- 
bination or  the  passage  of  an  electric  current  is  simply  a  kind  of  mechani- 
cal action;  in  the  one  case,  the  vibration  resulting  from  the  shock  of  mole- 
cules attracting  each  other;  in  the  other,  from  the  setting  up  of  a  wave 
movement,  or  kind  of  wave,  in  the  path  of  the  electric  disturbance,  what- 
ever that  may  be. 

That  heat  was  produced  by  mechanical  means  has  been  long  known. 
While  the  identity  of  heat  and  mechanical  force  was  suspected  by  Count 
Rumford  nearly  a  hundred  years  ago,  it  was  reserved  for  Joule  to  prove 
(by  long  continued  experiment),  that  the  same  quantity  of  work  always 
gave  the  same  quantity  of  heat,  and  to  Bankine  and  Clausius  to  show, 
theoretically,  that  the  same  quantity  of  heat  always  gives  the  same  amount 
of  work,  which  has  since  been  proved  beyond  all  doubt  by  experimental 
investigations. 

By  the  labors  of    the  two  great  men,  Rankine  and  Clausius,  the 


STEAM  USING;  OX,  STEAM  ENGINE  PRACTICE. 


science  of  thermodynamics  was  created, — the  application  of  mathematics 
it  the  laws  of  heat.  Of  this  interesting  and  beautiful  science  we  shall, 
however,  only  state  the  two  fundamental  principles: 

First  Principle — "Heat  and  mechanical  energy  are  mutually  convertible, 
"and  heat  requires  for  its  production  and  produces  by  its  disappearance 
"mechanical  energy  in  the  proportion  of  772  foot-pounds  for  each  British 
"unit  of  heat." 

The  British  unit  of  heat,  just  mentioned,  is:  "The  quantity  of  heat 
"which  corresponds  to  an  interval  of  one  degree  of  Farenheit's  scale  in  the 
"temperature  of  one  pound  of  pure  liquid  water  at  and  near  its  temperature 
"of  greatest  density  (39.1°F)." 

The  second  principle,  as  given  by  Clausius,  is  as  follows: 

Second  Principle. — "Heat,  of  itself,  never  passes  from  a  cold  body  to  a 
hotter  one." 

Kankine  states  the  second  principle  in  a  way  that  has  been  severely 
criticised  by  Maxwell,  but  which  appears  to  mean  that,  a  unit  of  heat  in  a 
cold  body  can  do  as  much  work  as  in  a  hot  body,  with  the  implied  reserva- 
tion that  there  must  be  yet  a  colder  body  into  which  it  may  pass. 

Heat  is  converted  into  mechanical  work  through  the  agency  of  some 
body  that  is  expanded  by  heat,  such  as  air  or  water.  The  heat  is  transferred 
into  these  mediums,  usually  enclosed  within  limits  of  changeable  volume, 
the  expanding  medium  enlarging  the  volume  against  a  resistance  thereby 
does  mechanical  work. 

It  has  been  taken  for  granted  that  the  word  temperature  was  under- 
stood to  have  its  ordinary  meaning,  and  that  neither  the  ordinary  thermo- 
metric  scales  of  temperature,  nor  the  ordinary  instruments  used  for  meas- 
uring temperature  required  description;  but  when  great  accuracy  was 
required,  the  use  of  the  air  thermometer  drew  attention  to  a  very  con- 
venient scale.  Dry  air  and  some  of  the  other  gases  increase  in  volume  or 
pressure  from  the  temperature  of  melting  ice  to  that  of  boiling  water  under 
the  atmospheric  pressure  as  follows: 

From  the  volume  or  pressure  1  to: 


Constant  Volume. 


Constant  Pressure. 


Air  

L  3665 

3670 

Hydrogen. 

I  3667 

3661 

Nitrogen  

3668 

Carbonic  Acid 

3688 

3669 

Carbonic  Oxide  .  . 

3667 

3719 

Nitrous  Oxide    . 

3676 

3719 

Cyanogen  

3829 

3877 

Sulphurous  Acid  

.3843 

.3903 

NOTE.— The  above  ratios  are  from  Reenault. 

With  the  air  thermometer  the  change  in  volume  of  a  portion  of  dry  air 
was  used  to  measure  the  change  in  temperature,  and  the  natural  result  was 
that  the  temperature  at  which  the  dry  gas  would  have  no  volume,  if  the 
law  should  hold  so  far,  was  taken  as  the  zero  or  starting  point  of  such  a 
scale.  This  zero  is  —461°  F.  or  —273°  C.,  and  is  called  "absolute  zero,"  and 


XA  TURE  OF  HE  A  T  AND  PROPERTIES  OF  STEAM.  3 

temperatures  measured  on  this  scale  are  called  "absolute  temperatures." 
We  shall  give  later  another  and  better  reason  for  this  scale  and  its  name, 
for  we  know  now  that  all  the  gases  above  given  can  be  reduced  to  liquids 
and  solids  and  therefore  are  not  perfect  gases. 

A  perfect  or  "reversible"  engine  was  devised  by  Sadi  Carnot;  and 
although  such  an  engine  cannot  be  constructed,  and  if  constructed,  could 
not  be  worked;  still  it  is  extremely  useful  in  assisting  our  conceptions  and 
in  giving  us  a  limit  beyond  which  we  cannot  hope  to  proceed  with  im- 
provements. 

The  operation  of  the  Carnot  engine  is  as  follows:  From  a  hot  body,  at 
temperature  Tlt  a  working  body  receives  heat  at  the  same  temperature  Tlt 
expanding  and  doing  work  from  the  heat  in  the  hot  body  directly.  After 
a  time  the  hot  body  is  withdrawn,  leaving  the  working  body  at  the  same 
temperature  Tlt  and  it  then  expands  by  virtue  of  the  heat  which  it  contains 
until  its  temperature  has  fallen  to  T2.  In  expanding,  more  work  has  been 
effected,  which,  of  course,  goes  to  the  credit  of  the  engine  as  work  done. 
At  the  temperature  T2,  the  working  body  is  brought  into  contact  with  a 
body  called  the  "cold  body,"  at  the  same  temperature  T2-,  work  is  then  done 
on  the  working  body  from  the  outside  in  compressing  it  to  such  a  point, 
heat  meanwhile  passing  from  the  working  body  to  the  cold  body  at  the 
same  temperature.  So  that  by  continuing  the  process  of  compression  after 
the  removal  of  the  cold  body,  the  working  body  will  have  just  reached  its 
first  state  of  volume,  pressure  and  temperature;  the  work  expended  in 
the  two  compression  processes  is,  of  course,  to  the  debit  of  the  engine,  but 
there  is  on  the  whole  a  balance  of  work  done  by  the  engine. 

It  can  be  shown  in  this  case,  whatever  be  the  working  substance 
used:  First.—  That  this  engine  utilizes  more  heat  than  can  be  utilized  by 
any  other  kind  of  engine  working  between  the  same  temperatures  2\  and 
T2.  Second.  —  That  the  work  done,  or  heat  utilized,  is  to  the  heat  expended 
from  the  hot  body,  as  the  difference  between  the  temperatures  between 
which  the  engine  works,  T,  —  !F2  is  to  the  absolute  temperature  of  the  hot 
body  jP,.  Hence  the  fraction 


2*1 

where  T  is  an  absolute  temperature,  is  known  as  the  efficiency  of  the 
engine,  and  is  the  maximum  efficiency  which  can  be  reached  by  theory. 

The  proof  of  the  above  statements  is  given  in  any  work  on  thermody- 
namics, so  that  we  shall  not  enter  upon  it  here,  believing  it  out  of  place 
in  a  work  of  a  practical  character. 

From  the  properties  of  the  Carnot  engine,  a  scale  of  temperature, 
based  upon  the  work  done  by  a  body  when  Tx  —  T2  =  1°,  is  established; 
and  it  has  been  shown  that  the  scale  thus  established  coincides  in  origin 
and  amount  with  that  of  the  perfect  gas  thermometer,  which  places  it  upon 
a  more  substantial  basis. 

When  heat  is  put  into  any  body  it  may  either  increase  the  agitation  of 
its  molecules,  thereby  heating  it  or  raising  its  temperature;  or  it  may  ex- 
pand it  against  an  external  resistance  doing  external  work;  or  it  may1 


4  STEAM  USING;  OB,  STEAM  ENGINE  PRACTICE. 

change  its  condition,  overcoming  molecular  attractions,  doing  what  is 
called  internal  work;  or  it  may  do  two  or  three  of  these  three  things  at  the 
same  time. 

When  a  fire  is  lighted  under  a  boiler  containing  cold  water,  the  heat 
generated  by  the  chemical  action  of  combustion  passes  from  the  fire  and 
the  gaseous  products  of  combustion  to  the  iron  of  the  boiler,  through  the 
iron  of  the  boiler  to  the  surface  in  contact  with  the  water  and  thence  into 
the  water.  The  volume  of  the  water  slightly  increases  with  the  tem- 
perature, raising  the  level  partly  by  its  own  increase  in  volume  and  partly 
by  the  increase  in  volume  of  the  air  contained  in  the  water.  The  heat 
increases  the  molecular  agitation  of  the  water,  till,  usually  at  the  tempera- 
ture of  212°  F.,  the  boiler  begins  to  make  steam.  If,  as  in  many  of  the 
boiler  trials,  the  man-head  or  safety  valve  is  open;  or,  as  in  a  common  tea 
kettle,  there  is  no  other  pressure  than  that  of  the  air  upon  the  water,  at 
this  temperature  the  water  remains;  and  all  the  heat  going  into  it  is 
expended  in  overcoming  the  molecular  attraction  of  one  atom  of  water 
for  another,  and  in  forcing  the  molecules  apart.  In  thus  overcoming  the 
molecular  attraction  it  is  doing  internal  work,  and  at  the  same  time  in  lift- 
ing the  atmosphere  by  the  steam  formed,  it  is  performing  external  work. 

When  the  quantities  of  heat  which  a  pound  of  water  requires  to  raise  it 
from  the  temperature  of  melting  ice  into  steam  at  any  given  pressure  are 
measured,  that  which  it  takes  to  raise  the  temperature  is  not  exactly  the  dif- 
ference in  the  temperatures  which  would  be  required  if  the  specific  heatof 
water  were  constant,  but  a  unit  of  heat  raises  the  temperature  of  a  pound 
of  water  a  little  less  than  one  degree  at  the  higher  temperatures.  When  a 
boiler  is  making  steam  at  a  given  pressure  other  than  that  of  the  atmos- 
phere, there  is  a  temperature  at  which  steam  forms  from  the  water  and 
above  which  the  water  cannot  be  raised.  This  is  known  as  the  tempera- 
ture of  evaporation  for  the  pressure.  It  is  to  be  noted  that  the  pressure  of 
the  atmosphere  may  be  partly  removed  and  low  pressure  steam  formed  at 
less  than  atmospheric  pressure. 

The  quantity  of  heat  required  to  evaporate  a  unit  of  weight  of  water 
at  different  pressures,  and  to  raise  the  temperature  up  to  that  of  evapora- 
tion, was  carefully  determined  by  Eegnault  in  an  extensive  series  of 
experiments  made  at  the  expense  of  the  French  Government.  The  volume 
of  one  pound  weight  of  steam,  and,  of  course,  its  reciprocal,  the  density  or 
weight  of  a  cubic  foot  of  steam,  was  determined  by  experiments  made  by 
Fairbairn  and  Tate. 

From  the  heat  of  evaporation,  the  volume  of  steam,  the  pressure  under 
which  it  was  evaporated,  and  the  volume  of  the  water  from  which  it  was 
formed  are  computed: 

First. — The  external  work  in  foot-pounds,  or  the  product  of  the  pres- 
sure in  pounds  per  square  foot  by  the  difference  in  cubic  feet  of  the  volume 
of  one  pound  of  steam  and  one  pound  of  water. 

Second.— The  external  work  in  heat  units  obtained  by  dividing  the  ex- 
ternal work  in  foot-pounds  by  772. 


.V.  I  y/  '/,'/•;  OF  ///•;.  I  T  A  XT)  PROPERTIES  OF  STE.  1 M.  5 

Third. — The  internal  work  of  evaporation  obtained  by  deducting  from 
the  heat  of  evaporation  the  external  work  found  above. 

Fourth. — The  sum  of  the  internal  work  of  evaporation  and  the  heat 
expended  in  raising  the  temperature, — sometimes  called  the  total  internal 
heat. 

Fifth. — The  sum  of  the  heat  expended  in  raising  the  temperature  of  the 
water,  and  the  heat  of  evaporation;  or,  the  sum  of  the  total  internal  heat 
and  the  external  work  in  heat  units;  or,  the  sum  of  the  heat  expended  in 
raising  the  temperature,  in  internal  work  of  evaporation  and  in  external 
work,  is  called  the  total  heat.  These  quantities  may  all  bo  stated  in  foot- 
pounds, and  some  writers  prefer  to  use  them  in  this  way.  But,  although  the 
measurement  of  mechanical  work  is  usually  made  in  foot-pounds,  all  meas- 
urements of  heat  and  steam  which  require  measurements  of  temperature 
are  best  made  with  a  thermometer,  and  by  heat  units;  we  shall,  therefore, 
retain  the  heat  units.  There  is  also  this  advantage,  that  in  computation 
there  will  be  smaller  numbers  and  less  figures  involved. 

The  measurement  of  the  heat  expended  in  raising  the  temperature  of 
water,  in  the  total  internal  heat  and  the  total  heat,  are  all  based  on  a  start- 
ing point  of  one  pound  of  water  at  the  temperature  of  melting  ice.  As,  how- 
ever, such  quantities  are  usually  used  by  differences,  many  writers  give 
these  data  from  0°  F.  Of  course  this  does  not  require  any  real  existence 
to  the  imaginary  pound  of  water,  as  water  assumed  in  this  way.  It  gives 
a  little  less  numerical  work  with  feed  water  at  low  temperature,  but  is  of 
no  help  when  the  specific  heat  has  varied  so  as  to  alter  the  heat  expended 
in  raising  the  temperature  of  the  water  from  the  difference  between  the 
temperature  and  32°.  We  adhere  to  the  basis  of  melting  ice. 

Most  of  the  theoretical  writers  use  as  a  base  for  the  tables  the  temper- 
ature of  evaporation,  although  others  use  the  pressure, — a  much  more 
practical  starting  point  for  engineers.  But  these  writers  have  not  given 
the  internal  and  external  heats,  have  used  in  some  cases  the  0°  F.  start- 
ing point  referred  to  above,  and  have  given  extended  decimals.  In  our  own 
table  we  have  only  given  the  nearest  heat  unit,  and  have  given  a  table,  not 
for  every  pound  of  pressure,  it  is  true,  but  one  in  which  it  is  very  easy  to 
interpolate  the  nearest  unit.  We  believe  this  table  to  be  convenient  for 
use  and  sufficiently  extended  and  accurate. 

The  heat  of  evaporation  is  called  latent  heat  of  evaporation,  but  as  the 
term  latent  has  now  no  meaning  we  shall  not  retain  it. 

As  the  Kegnault  experiments  on  steam  are  always  considered  models 
in  every  respect,  and  as  being  of  unapproachable  accuracy,  we  shall  only 
say  that  they  were  made  in  all  circumstances  and  conditions  in  a  thoroughly 
practical  way,  and  that  the  values  reached  have  been  computed  from  purely 
theoretical  grounds;  so  also  with  densities.  The  table  is  to  be  relied 
upon,  and  we  shall  not  explain  the  experiments  or  comment  further  upon 
them,  but  will  illustrate  by  a  few  examples  the  use  of  the  table  here  given: 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


TABLE  I.— THE  PROPERTIES  OF  SATURATED  STEAM. 


Pressure  in  Ibs. 
per  sq.  inch 
above  the  at- 
mosphere. 

Temperature 
of  steam  in 
degrees  Fah- 
renhejt. 

Heat  above  32° 
F.  in  water 
at  boiling 
point. 

External  work 
in  heat  units. 

H 

Internal  work 
of  evaporat'n 
in  heat  units. 

Latent  heat  of 
evaporat'n  in 
heat  units. 

1  **  * 
.2  eo 

.2  «  • 
.g  5 

Weight  of  1  cu. 
ft.  of  steam 
in  pounds. 

Volume  of  1  It), 
in  cubic  feet. 

—14 

90 

1109 

—13 

121 

99 

62 

1118 

967 

1029 

3 

0.006 

172.0 

—12 

138 

106 

65 

1124 

943 

1018 

0.008 

117.5 

—11 

160 

118 

67 

1127 

942 

1009 

d 

0.011 

89.6 

—10 

160 

128 

67 

1130 

935 

1002 

3 

.014 

72.6 

—  9 

168 

136 

67 

1133 

925 

993 

<u  . 

.016 

61.2 

—  8 

175 

143 

68 

1134 

923 

991 

,Qg 

.019 

52.9 

—  7 

181 

150 

68 

1137 

918 

987 

.021 

46.7 

—  6 

187 

156 

69 

1138 

913 

982 

a  «8 

.024 

41.8 

ft 

—  5 

192 

161 

69 

1140 

909 

979 

.026 

37.8 

—  4 

196 

165 

70 

1141 

906 

976 

V-rl 

.029 

34.6 

—  3 

201 

170 

70 

1143 

903 

973 

5  S 

.031 

31.8 

—  2 

205       174 

71 

1144 

899 

970 

j_i  o 

.034 

29.5 

—  1 

209 

178 

71 

1145 

896 

967 

5 

.036 

27.6 

0 

212 

181 

72 

1146 

893 

965 

1074 

.038 

26.3 

1 

215 

184 

72 

1147 

890 

962 

1074 

.041 

24.3 

2 

219 

188 

72 

1148 

888 

960 

1076 

.043 

23.0 

3 

222 

191 

73 

1149 

887 

958 

1078 

.046 

21.8 

4 

225 

194 

73 

1150 

885 

956 

1079 

.048 

20.7 

5 

227 

196 

73 

1151 

882 

953 

1079 

.050 

19.7 

6 

230 

199 

74 

1152 

879 

951 

1079 

.053 

18.8 

7 

233 

202 

74 

1152 

877 

950 

1079 

.055 

1S.O 

8 

235 

204 

74 

1153 

876 

948 

1079 

.058 

17.2 

9 

237 

206 

74 

1154 

873 

947 

1080 

.060 

16.6 

10 

239 

208 

74 

1154 

872 

945 

1080 

.062 

16.0 

11 

242 

211 

75 

1155 

869 

944 

1080 

.065 

15.4 

12 

244 

213 

75 

1156 

867 

942 

1080 

.067 

14.9 

13 

246 

215 

75 

1156 

866 

941 

1081 

.070 

14.4 

14 

248 

217 

75 

1157 

864 

939 

1081 

.072 

13.9 

15 

250 

220 

75 

1158 

863 

938 

1083 

.074 

13.4 

16 

252 

222 

75 

1158 

862 

937 

1083 

.076 

13.0 

17 

254 

224 

76 

1159 

859 

935 

1084 

.079 

12.7 

18 

256 

226 

76 

1159 

858 

934 

1084 

.081 

12.3 

19 

257 

227 

76 

1160 

857 

933 

1084 

.083 

12.0 

20 

259 

229 

76 

1160 

856 

932 

1085 

.086 

11.6 

22 

262 

232 

76 

1161 

853 

929 

1085 

.090 

11.0 

24 

266 

236 

77 

1162 

850 

927 

1086 

.095 

10.6 

26 

269 

239 

77 

1163 

848 

925 

1087 

.099 

10.0 

28 

272 

242 

77 

1164 

846 

923 

1088 

.104 

9.6 

30 

274 

244 

77 

1165 

844 

921 

1088 

.109 

9.2 

35 

281 

251 

78 

1167 

838 

916 

1089 

.120 

8  3 

40 

287 

257 

78 

1169 

834 

912 

1091 

.131 

7.G 

45 

293 

263 

78 

1171 

830 

908 

1093 

.142 

7.0 

60 

298 

268 

79 

1172 

825 

904 

1093 

.154 

6.& 

55 

303 

273 

79 

1174 

822 

901 

1095 

.165 

6.1 

60 

307 

278 

79 

1175 

818 

897 

1096 

.176 

5.7 

65 

312 

282 

80 

1176 

814 

894 

1097 

.187 

5.3 

70 

316 

287 

80 

1178 

811 

891 

1098 

.198 

5.0 

75 

320 

291 

80 

1179 

808 

888 

1099 

.209 

4.8 

80 

324 

294 

80 

1180 

806 

886 

1100 

.220 

4.5 

85 

328 

298 

81 

1181 

802 

883 

1100 

.231 

4.3 

90 

331 

301 

81 

1182 

800 

881 

1101 

.241 

4.1 

95 

334 

305 

81 

1183 

798 

878 

1101 

.252 

4.0 

100 

338 

308 

81 

1184 

795 

876 

1102 

.263 

3.8 

.Y.I  77  /,'/•;  OF  HEAT  AND  PROPERTIES  OF  STEAM. 


TABLE  I.— THE  PROPERTIES  OF  SATURATED  STEAM. 


Pressure  in  Ibs. 
per  sq.  inch 
above  the  at- 
mosphere. 

Temperature 
of  steam  in 
degrees  Fah- 
renheit. 

Heat  above  32° 
F.  in  water 
at  boiling 
point. 

External  work 
in  heat  units. 

Ik 

—   o> 

E88 

Internal  work 
of  evajjorafn 
in  heat  units. 

Latent  heat  of 
evaporat'nin 
heat  units. 

||| 

a  0 

^ITI 

Weight  of  1  cu. 
ft.  of  steam 
in  pounds. 

Volume  of  1  It), 
in  cubic  feet. 

165- 

341 

311 

82 

1185 

792 

874 

1103 

.274 

3.6 

110 

344 

315 

82 

1186 

789 

871 

1104 

.284 

3.5 

115 

34^ 

318 

82 

1187 

787 

869 

1105 

.295 

3  4 

120 

350 

321 

82 

1188 

785 

867 

1106 

.306 

3.3 

125 

353 

324 

82 

1189 

783 

865 

1107 

.316 

3.2 

130 

355 

327 

82 

1190 

781 

863 

1108 

.327 

3.1 

135 

358 

329 

82 

1191 

779 

861 

1108 

.338 

3.0 

140 

361 

331 

83 

1191 

777 

860 

1109 

.348 

2.9 

145 

363 

334 

83 

1192 

775 

858 

1109 

.359 

2.8 

150 

366 

337 

83 

1193 

773 

856 

1110 

.369 

2.7 

155 

368 

340 

83 

1194 

771 

854 

1111 

.380 

2.6 

160 

371 

341 

83 

1194 

770 

853 

1111 

.390 

2.6 

165 

373 

344 

83 

1195 

768 

851 

1112 

.400 

2.5 

170 

375 

347 

84 

1196 

765 

849 

1112 

.412 

2.4 

175 

377 

348 

84 

1196 

764 

848 

1113 

.422 

2.4 

180 

380 

351 

84 

1197 

762 

846 

1113 

.433 

2.3 

185 

382 

353 

84 

1198 

761 

845 

1114 

.443 

2.3 

195 

386 

357 

84 

1199 

758 

842 

1115 

.463 

2.2 

205 

390 

361 

85 

1200 

754 

839 

1115 

.484 

2.1 

215 

394 

365 

85 

1201 

751 

836 

1116 

.505 

2.0 

225 

397 

368 

85 

1202 

749 

834 

1117 

.525 

1.9 

235 

401 

373 

85 

1204 

746 

831 

1119 

.546 

1.8 

245 

404 

376 

85 

1205 

744 

829 

1120 

.567 

1.8 

255 

408 

380 

85 

1206 

741 

826 

1121 

.587 

1.7 

265 

411 

383 

85 

1207 

739 

824 

1122 

.608 

1.6 

275 

414 

386 

85 

1208 

737 

822 

1123 

.627 

1.6 

285 

417 

389 

86 

1209 

734 

820 

1123 

.649 

1.5 

335 

430 

392 

86 

1213 

725 

811 

1127 

.750 

1.3 

385 

445 

417 

86 

1217 

714 

800 

1131 

.850 

1.2 

435 

457 

428 

87 

1220 

705 

792 

1133 

.950 

1.05 

485 

467 

440 

87 

1224 

697 

784 

1137 

1.049 

0.95 

585 

487 

460 

87 

1230 

683 

770 

1143 

1.245 

0.80 

685 

504 

477 

88 

1235 

670 

758 

1147 

1.439 

0.69 

785 

519 

493 

88 

1240 

659 

747 

1152 

1.632 

0.61 

885 

534 

507 

88 

1244 

649 

737 

1156 

1.823 

0.55 

985 

516 

520 

88 

1248 

640 

728 

1160 

2.014 

0.50 

Values  below  *  *  *  are  computed  and  not  experimental. 

NOTE.— For  all  values  of  Total  Internal  work  below  the  atmosphere  1070  heat  units 
may  be  taken.  All  decimal  parts  of  heat  units  have  been  neglected  and  the  last  one 
may  therefore  be  in  error. 

Example  /.—How  much  more  heat  is  needed  to  boil  a  pound  of  water 
at  200  pounds  per  square  inch  boiler  pressure  than  at  five  pounds  per 
square  inch,  the  feed  being  at  60°  F.  in  either  case. 

AT  FIVE  POUNDS. 

Units. 

Heat  required  to  raise  1  pound  water  from  32°  to  boiling  at  5  pounds  pressure 196 

Deduct  heat  to  raise  from  32°  to  60°  not  used .' 28 

'  

Heat  to  raise  from  60°  to  boiling 168 

Internal  work  of  evaporation.* 882 

External  work  of  evaporation 73 

Heat  required  to  boil  from  feed  at  60°  at  5  pounds 1,123 


8  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

AT  TWO  HUNDRED  POUNDS. 

Units. 

Heat  required  to  raise  1  pound  water  from  32°  to  boiling  at  200  pounds  per  sq.  inch. .    359 
Deduct  heat  to  raise  from  32°  to  60°  not  used 28 

331 

Internal  work 756 

External  work . 84 

1,171 

Heat  required  to  boil  1  pound  of  water  from  feed  at  60°  at  200  pounds: 
1,171  —  1,123  =  48  units. 

j-|L  =  4  per  cent.,  nearly. 

The  same  result  could  be  reached  more  directly. 

Units. 

Total  heat  from  32°  at  200  pounds 1,199 

Total  heat  from  32°  at  5  pounds 1,161 

Difference 48 

Deducting  from  the  1,151  the  28  units  not  used,  from  32°  to  60°,  the  feed 
being  at  60°,  we  have  1,123  for  the  divisor  to  reduce  to  per  cent,  as  before. 

We  advise  the  reader  to  use  the  former  method,  by  preference,  in  his 
computations,  as  serving  to  keep  in  full  view  the  different  uses  and  the  va- 
rious amounts  of  heat  required  for  them;  although  there  is,  of  course,  more 
numerical  work  required  to  do  so. 

The  reason  so  much  more  difficulty  is  experienced  in  maintaining 
high  pressure  than  low  pressure  steam  is  to  be  found,  not  in  the  boiling  of 
equal  weights  of  water,  but  in  the  fact  that  the  high  pressure  steam 
leaves  the  boiler  more  easily.  If,  for  example,  it  be  employed  in  an 
engine,  the  engine  can  be  made  to  do  more  work  thereby.  If,  in  running 
a  boat,  the  boat  going  faster  the  engine  uses  more  steam;  if  employed 
in  heating  a  building,  the  radiators  act  more  energetically  with  the  higher 
pressure,  transmit  more  heat,  condense  more  steam,  and  the  skillful 
attendant  suits  his  fire  to  the  work. 

Example  //.—How  much  saving  of  fuel  can  be  made  by  raising  the 
temperature  of  the  feed- water  from  100°  F.  to  200°  F.,  the  boiler  pressure 

being  120  pounds  per  square  inch. 

Units. 

Total  heat  for  120  pounds 1,188 

Deduct  in  the  one  case  the  units  not  used  in  raising  the  water  from  32°  F.  to  100°  F . .     68 

Required  from  100°  F.  to  boil  at  120  pounds 1,120 

In  the  other  case  deduct  for  not  using  from  32°  to  200° 169 

Required  to  boil  at  120  pounds  from  water  at  200°  F 1,019 

Difference  between  1,120  and  1,019  is  101  units,  or  about  9  per  cent. 
In  order  to  compare  the  performance  of  different  boilers  working  with 
different  pressures  and  fed  with  water  at  different  temperatures,  it  is  ne- 
cessary to  assume  a  standard  pressure,  temperature  of  evaporation,  and 
temperature  of  feed-water.  Various  temperatures  of  feed-water  have  been 
used,  0°  F.,  32°  F.,  100°  F.,  the  latter  about  the  usual  temperature  of  feed- 
water  for  condensing  engines,  and  212°  F.,  used  more  generally  than  any 
of  the  others  as  a  standard;  while  for  the  pressure  and  temperature  of 
evaporation  the  atmospheric  pressure  and  212°  F.  are  usually  taken. 


NATURE  OF  HEAT  AND  PROPERTIES  OF  STEAM.  9 

Example  III. — By  experiment  with  a  boiler  at  160  pounds  per  square 
inch  it  was  found  that,  one  pound  of  coal  evaporated  7.91  pounds  of  water. 
The  temperature  of  the  feed- water  was  noted  at  120°  F.:  required  the 
equivalent  evaporation  from  and  at  212°  F. 

Units. 

Total  heat  of  evaporation  from  32°  F.  at  160  pounds 1,194 

Deduct  from  32°  to  120°,  units  not  used 88 

Heat  to  evaporate  from  30°  at  160  pounds 1,106 

Internal  heat  of  evaporation  at  212° 893 

External  work  of  evaporation  at  212° 72 

Sum  or  heat  of  evaporation  at  212° 965 

7.91  x  1>106  =  9.06  as  the  evaporation  required. 
965 

In  order  to  facilitate  this  computation  the  following  table  of  factors  of 
evaporation  is  given: 


10 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


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•*  «  -;  <N  e*i  TH  rH  o  o  ci  en  oo  oo  i-  c-  ee  o  m  >n  -*  eo  co  o»  <N  rH  rn  001 


I  t-  IN  t-  <M  t- 

SS8§  g 


s  1-1  vc  o  w  o  »o  o  "io'ci  ^  cr,  •*  e>  co  oo  co  x  co  t-  <N  t-  ^  t-  rH  o  rH  o  rH  in  o  m  o  >n  o  10 

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8  H 


c- <N  «o  rH  «o  rn  o  o   in  o  o  o  m 

SSS  ooooo  ooooo 


SS 


CCC-  C^t— 


i  iilll  lllii  I 


S  ISSSS  ISSS3  Slip  Slsis  liiil  iilll  ISIsI  S 


lliiiisssaa  sssas  sins 


S     Hill     SrlSSrH     SSrHrnS     SSlll     Illll     §1111     11§S8     II 


3,'ATUJiE  OF  SEAT  AND  PROPERTIES  OF  STEAM. 


11 


The  use  of  this  Table  of  Factors  of  Evaporation  is  readily  seen  by  tak- 
ing the  last  example.  The  boiler  evaporating  7.91  pounds  at  160  pounds 
per  square  inch  from  feed  at  120°  F.,  th3  evaporation  factor  from  Table 
II.  for  120°  and  160  pounds  is  1.146.  7.91  x  1.146  =  9.06,  as  before,  for  the 
equivalent  evaporation  from  and  at  212°  F. 

We  introduce  one  other  table  here— the  weight  of  1  cubic  foot  of  water 
at  different  temperatures.  Very  often  in  the  trials  of  a  boiler  or  engine 
the  most  convenient  unit  of  measurement  of  water  is  the  cubic  foot.  This 
will  be  the  case  when  a  weir  measurement  is  made  or  when  the  water  is 
measured  by  a  water  meter.  The  use  of  a  water  meter  involves  many  pre- 
cautions, the  most  important  being  the  following:  The  meter  should  work 
under  moderate  head  of  supply  and  small  head  of  delivery;  it  should  be 
set  in  such  a  manner  that  it  can  be  tested  in  place  under  the  exact  condi- 
tions of  use;  if  a  positive  meter,  it  should  be  especially  constructed  to 
work  freely,  if  it  is  to  be  used  in  warm  water.  This  table  is  also  used  for 
estimating  the  weight  of  water  in  boilers,  and  for  correcting  boiler  trials 
for  differences  of  water  level. 

TABLE    HI.—  EXPANSION   AND    DENSITY    OF   PURE    WATER. 
FROM  D.  K.  CLARK  AND  BY  RANKINE.  APPROXIMATE  FORMULA. 


Temperature  in  degrees 

COMPA 

BATTVE. 

Density   of    Weight 

Fahrenheit. 

Volume. 

Density. 

per  Cubic  Foot. 

32 

1.00000 

1.00000 

62.418 

35 

1.99993 

.00007 

62.422 

39.1 

1.99989 

.00011 

62.425 

40 

1.99983 

.00011 

62.425 

45 

1.99993 

.00007 

62.422 

46 

.00000 

1.00000 

62.418 

50 

.00015 

.99985 

62.409 

52.3 

.00029 

.99971 

62.400 

55 

.00038 

.99961 

62.394 

60 

.00074 

.99926 

62.372 

62 

.00101 

.99899 

62.355 

65 

.00119 

.99881 

62.344 

70 

.00160 

.99832 

62.313 

75 

.00239 

.99771 

62.275 

80 

.00299 

.99702 

62.232 

85 

.00379 

.99622 

62.182 

90 

.00459 

.99543 

62.133 

95 

.00554 

.99449 

62.074 

100 

.00639 

.99365 

62.022 

ioa 

.00739 

.99260 

61.960 

:uo 

.00889 

.99199 

61.868 

115 

.00989 

.99021 

61.807 

120 

.01139 

.98874 

61.715 

125 

.01239 

.98808 

61.654 

130 

.01390 

.98630 

61.563 

135 

.01539 

.98484 

61.472 

140 

.01690 

.98339 

61.381 

145 

.01839 

.98194 

61.291 

150 

.01989 

.98050 

61.201 

155 

.02164 

.97802 

61.0% 

160 

.02340 

.97714 

60.991 

165 

.02589 

.97477 

6H.843 

170 

.02690 

.97380 

60.783 

12 


STEAM  USING;  Oil,  STEAM  ENGINE  PRACTICE. 


TABLE  III.— CONTINUED. 


Temperature  in  degrees 
Fahrenheit. 

COMPARATIVE. 

Density   of    Weight 
per  Cubic  Foot. 

Volume. 

Density. 

175 
180 

1.02906 
1.03100 

.97193 
.97006 

60.655 
60  .548 

185 
190 
195 
200 
205 

1.03300 
1.03500 
1.03700 
1.03889 
1.0414 

.96828 
.96632 
.96440 
.96256 
•  9602 

60.430 
60.314 
60.198 
60.081 
59.93 

210 
212  by  formula. 
212  by  measurement. 

1.0434 
1.0444 
1.0466 

.9584 
.9575 
.9555 

59.82 
59.76 
59.64 

230 
250 
270 
290 

1.0529 
1.0628 
1.0727 
1.0838 

.9499 
.9411 
.9323- 
.9227 

59.36 
58.78 
58.15 
57.59 

298 
338 
366 
390 

1.0899 
1.1118 
1  .  1301 
1  .1444 

.9175 
.8994 
.8850 
.8738 

57.27 
56.14 
55.29 
54.54 

The  use  of  the  table  of  the  properties  of  steam  is  more  frequent  in  the 
study  of  engine  performance  and  indicator  diagrams  than  of  boiler  per- 
formance, but  there  is  an  important  point  in  determining  the  evaporation 
of  a  boiler  in  which  it  becomes  of  use. 

As  bubbles  of  steam  formed  on  the  hot  iron  of  a  boiler  rise  through 
the  water  to  the  surface,  breaking  and  scattering  spray,  a  portion  of  water 
thus  thrown  up  into  the  steam  room  is  carried  along  with  the  steam,  and 
unless  more  heat  be  supplied  to  evaporate  this  water  it  increases  the  volume 
caused  by  the  steam  condensed  in  the  pipes  in  the  upper  portion  of  the 
boiler.  This  water  carried  with  the  steam  is  said  to  be  "entrained"  with  it 
and  is  called  "priming"  by  many  writers.  When  the  proportion  of  water 
becomes  so  large  as  to  be  evident  in  the  action  of  the  engine  or  the  exhaust, 
it  is  usually  called  by  engineers  "foaming."  The  amount  of  such  water  is 
increased  if  the  water  is  dirty  and  covered  with  scum,  or  if  grease  and  alkali 
combine  to  form  a  soap.  The  amount  of  water  which  can  be  carried  by 
steam  in  suspension  is  very  great,  but  depends  somewhat  upon  the  velocity 
of  the  current  of  steam;  if  the  passages  are  large,  and  the  flow  of  steam  of 
moderate  velocity  the  water  has  time  to  drop  out  of  the  steam  by  the 
action  of  gravity.  (Iu  some  cases  the  amount  of  water  carried  in  weight 
has  been  known  to  be  three  times  that  of  the  steam  carrying  it,  although 
usually  it  does  not  exceed  10  to  15  per  cent. 

The  higher  the  pressure  of  steam  the  greater  its  density  and  the 
quieter,  other  things  being  equal,  is  the  process  of  ebullition  and  the  smaller 
the  quantity  of  entrained  water.  The  amount  of  water  thrown  up  in  spray 
is  largely  dependent  on  the  circulation,  being  much  diminished  by  im- 
provements in  that  direction.  The  area  of  surface  water  in  contact  with  the 
steam  seems  to  be  an  important  matter  according  to  some  authorities,  but 


NATURE  OF  HEAT  AND  PROPERTIES  OF  STEAM.  13 

as  this  varies  very  greatly  without  any  apparent  effect,  we  are  not  inclined 
to  attribute  much  importance  to  it.  A  violent  rush  of  steam  close  to  the 
top  of  a  body  of  water  is  to  be  avoided,  as  even  a  current  of  air  would 
throw  spray  in  such  a  case. 

The  accurate  determination  of  the  water  entrained  with  steam  is  a 
matter  of  great  difficulty  and  at  the  same  time  of  great  importance  in  the 
determination  of  the  performance  of  boilers  and  engines. 

Four  methods  have  been  devised  to  measure  the  amount  of  water  en- 
trained, and  two  of  them  have  been  used  in  practice. 

The  first  method,  that  of  M.  G.  A.  Him,  is  the  most  used.  It  depends 
upon  the  amount  of  heat  given  out  by  a  known  weight  of  a  mixture  of 
steam  and  water  and  is  best  performed  as  follows: 

A  barrel  is  set  on  a  platform  scale  and  a  known  weight  of  water  run 
into  it.  It  is  convenient  to  put  in  298  Ibs.  of  water.  Steam  is  taken  from 
the  top  of  the  steam  pipe  by  a  rubber  hose  terminated  by  an  iron  pipe 
capped  on  the  lower  end  and  perforated  with  holes  drilled  obliquely  to 
the  radii,  but  in  the  plane  thereof.  .  This  pipe  is  placed  in  the  barrel  of 
water  and  steam  turned  on;  the  scale  is  loaded  2  Ibs.  more,  and  as  the 
steam  comes  into  the  water  the  fluid  increases  in  weight,  and  when  the 
beam  tips  there  is  300  Ibs.  of  water.  The  temperature  of  the  water  is  then 
carefully  noted.  The  disposition  of  the  jets  keeps  the  water  stirred  up 
thoroughly,  and  the  flow  of  steam  into  the  water  being  horizontal  only,  the 
water  remains  steady.  The  weight  is  then  increased  10  Ibs.,  and  when  the 
the  scale  tips  at  310  pounds  the  temperature  is  noted. 

The  number  of  heat  units  given  to  the  water,  in  the  barrel,  by  the 
steam  and  water  from  the  boiler,  is  found  by  multiplying  the  300  Ibs.  of 
water  by  the  rise  in  its  temperature. 

The  portion  which  was  dry  steam  gives  up  its  internal  heat  of  evapor- 
ation in  condensing,  and  the  external  work  done  by  the  air  upon  the  fluid 
in  compressing  it  from  steam  to  water,  together  make  the  latent  heat  of 
evaporation;  and  the  whole  fluid  then  falls  in  temperature  from  that  due 
to  the  pressure  in  the  boiler  to  the  final  temperature  of  the  barrel. 

Deducting  from  the  heat  gained  by  the  water  in  the  barrel,  ten  times 
the  difference  between  the  boiler  temperature  and  the  final  temperature 
in  the  barrel,  and  dividing  the  remainder  by  ten  times  the  latent  heat  at  the 
boiler  pressure,  the  quotient  will  be  the  fraction  of  the  whole  which  is  dry 
steam. 

It  is  easily  seen  that  with  any  other  weight  the  process  would  be  the 
same;  but  in  place  of  the  ten  we  should  use  the  number  of  pounds  run  in 
between  the  noting  of  the  temperatures. 

The  preliminary  2  Ibs.  is  to  provide  for  any  water  which  might  have 
collected  in  the  hose  or  connections  while  standing,  and  to  render  the  op- 
eration uniform. 

Sometimes  a  coil  of  pipe  as  a  surface  condenser  is  used,  and  the  steam 
which  is  condensed  therein  is  kept  separate  from  the  condensing  water; 
but  great  care  has  to  be  used  to  get  all  the  water  condensed  out  of  the  coil. 
The  accuracy  of  this  method  is  dependent  upon  the  delicacy  of  weighing 


14  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

and  the  reading  of  the  thermometer;  in  unskillful  hands  the  results  are 
sometimes  astonishing. 

The  second  method  is  to  put  into  the  feed  water  a  quantity  of  sulphate 
of  soda,  and  to  draw  from  the  boiler,  at  intervals,  from  the  lower  gauge  cock 
a  small  amount  of  water,  keeping  this  water  by  itself;  also  to  draw  from  the 
steam,  condensing  either  by  a  coil  of  pipe  in  water,  or  a  small  pipe  in  air, 
taking  care  to  draw  only  water  without  steam,  at  the  same  intervals,  keep- 
ing the  one  separate  from  the  other.  A  chemical  analysis  defines  the  pro- 
portion of  sulphate  of  soda  in  each  portion,  and  a  division  of  the  proportion 
of  sulphate  of  soda  in  the  portion  from  the  steam  by  the  proportion  in  that 
from  the  water  gives  the  proportion  of  water  entrained,— the  basis  of  the 
method  being  the  fact  that  steam  does  not  carry  the  sulphate  of  soda, 
this  being  only  carried  by  the  hot  water  entrained.  This  method  was  used 
by  Professor  Stahlschmidt  at  the  DusseldOrf  Exhibition  Boiler  Trials. 

A  third  method  has  been  suggested:  To  enclose  a  portion  of  steam  in  a 
vessel  placed  inside  the  steam  pipe,  then  closing  it  and  removing  it  from 
the  steam  pipe,  obtain  the  weight  of  the  enclosed  fluid,  which,  being 
in  a  known  volume,  the  proportion  of  water  can  be  found  from  the  volume 
and  density  at  the  known  pressure.  There  appear  to  be  many  practical 
difficulties  in  this  method,  and  we  are  not  aware  that  it  has  been  used  to 
any  extent. 

A  fourth  method  is  to  have  a  small  cylinder  with  piston  enclosed  in  the 
steam,  and  to  put  a  known  volume  of  the  cylinder  in  connection  with  the 
steam;  then  closing  the  communication,  pull  out  the  piston  (which, 
of  course,  passes  through  proper  stuffing  boxes  into  the  air)  until  the 
pressure  in  the  cylinder  begins  to  lower, — the  water  contained  evapor- 
ating at  the  pressure,  until,  after  it  has  been  evaporated  the  pressure  begins 
to  fall  with  increase  of  volume.  The  increase  of  volume  at  constant  pres- 
sure divided  by  the  final  volume  is  the  proportion  of  water  carried.  This 
method  promises  well,  but  we  have  no  knowledge  of  its  use. 

Steam  formed  in  the  presence  of  water  is  always  saturated,  that  is,  it  is 
at  the  same  temperature  as  the  water,  and  cannot  be  raised  above  that  tem- 
perature until  the  water  is  all  evaporated;  but  after  this  has  been  done,  or 
if  the  steam  be  heated  in  a  separate  vessel,  the  temperature  rises  nearly 
2°  F.  for  each  unit  of  heat  added  to  a  pound  in  weight,  while  the  steam 
increases  in  volume  at  first  not  very  closely,  but  afterwards  very  nearly  as 
a  perfect  gas,  or  by  ^-s  part  of  itself  for  each  degree  F.  The  amount  of 
heat  required  to  raise  1  ft.  weight  of  dry  steam  1°  F.,  is  stated  as  0.47  of  a 
unit,  and  0.5  by  different  authorities,  the  first  including  Kankine,  and  the 
second  Hirn.  Steam  thus  raised  in  temperature  is  said  to  be  superheated, 
but  our  knowledge  of  this  condition  is  still  very  limited  and  confined  to 
the  results  of  a  few  experiments. 


CHAPTER      II. 

ON  VALVE  GEAR. 

As  steam  can,  only  do  useful  work  by  changing  the  volume  of  the 
vessel  enclosing  it,  we  find  that  to  employ  it  in  moving  a  piston  in  a  cyl- 
inder is  the  most  practical  method  of  using  it.  There  is,  however,  a  cer- 
tain class  of  pumping  engines,  in  which  steam  in  direct  contact  with  a 
fluid,  without  intervening  mechanism,  is  used  for  pumping  water. 

The  motion  of  the  piston  to  and  fro  in  the  cylinder  is  communicated 
to  the  outside  of  the  cylinder  by  a  rod  passing  through  a  steam-tight 
opening,  where  it  is  then,  in  some  way,  connected  to  the  resistance  which 
is  to  be  overcome,  either  directly  as  to  a  pump  rod,  or  indirectly  by  a 
connecting  rod  and  crank  to  a  rotating  shaft,  which  is  to  be  revolved 
against  the  resistance. 

The  steam  has  to  be  let  in  and  out  of  one  or  both  ends  of  the  closed 
cylinder,  and  for  this  purpose  there  are  used  one,  two,  three,  or  four 
valves,  which  open  and  close  two  or  four  passage  ways,  or  ports. 

These  valves  are  moved  by  mechanism  of  more  or  less  complex 
form  by  the  engine  itself,  and  are  either  slides,  lifting  valves,  or  rotative 
valves. 

The  use  of  the  slide  valve  and  eccentric  requires  little  illustration 
until  we  examine  them  more  closely. 

The  piston  of  the  engine  is  connected  to  the  piston  rod,  which  passes 
out  of  the  cylinder,  and  is  fastened  to  the  cross- head,  and  this  can  only 
move  in  a  straight  line.  The  connecting  rod  is  attached,  at  one  end,  to 
the  cross-head  by  a  pin  and  suitable  box,  and  at  the  other  end  to  the 
crank  pin;  thus,  one  end  of  the  connecting  rod  can  only  move  in  a 
straight  line  while  the  other  end  moves  in  a  circle. 

The  action  of  the  slide  valve  by  the  eccentric  is  in  a  similar  manner — 
one  end  of  the  eccentric  rod  moving  in,  or  nearly  in,  a  straight  line,  while 
the  other  end  moves  in  a  circle;  for,  it  must  not  be  forgotten  that  the 
eccentric  may  be,  and  sometimes  is,  defined  as  a  crank  with  a  small  crank 
arm  and  large  crank  pin. 

It  is  well  known  that  the  motion  of  the  two  ends  of  the  connecting 
rod  is  not  regular;  that  is  to  say,  that  for  equal  movements  of  the  piston 
equal  ones  are  not  moved  over  by  the  crank,  and  further,  that  for  equal 
distances  moved  by  the  piston  from  the  end  of  the  stroke,  the  angles 
moved  over  by  the  crank  from  the  dead  points  are  not  alike;  and,  also, 
for  equal  arcs  moved  by  the  crank,  the  cross-head  aijd  piston  move 
unequal  distances.  This  is  shown  in  Fig.  2,  where  the  arcs  0-1  is  equal  to 
6-7,  1-2  equal  to  5-6,  and  2-3  equal  to  4-5,  but  the  distances  on  the  straight 
line  between  points  with  the  same  numbers  are  evidently  not  equal. 


16 


STEAM  rSING;  OK,  STEAM  ENGINE  PRACTICE. 


fL\  VALVE  fiEAli. 


17 


An  examination  of  this  irregularity  shows  us  that  it  increases  as  the 
lengths  of  the  connecting  rod  and  crank  are  more  nearly  equal,  and 
decreases  the  more  unequal  they  are.  Now  for  any  engine,  the  lengths  of 
the  connecting  rod  and  crank  are  more  nearly  equal  than  the  eccentric 


o  i 


FIG.  2. 


rod  and  eccentric  radius  for  the  same  engine,  and  if  the  latter  are  50 
inches  and  2  inches  long,  respectively,  the  greatest  error  introduced  by 
them  is  less  than  0.005  inch.  We  should  be  justified  in  neglecting  this 
entirely,  but  we  must  remember  that  we  can  not  do  so  for  the  irregularity 
due  the  connecting  rod  and  crank;  and  it  becomes  convenient  for  us  to 
refer  the  position  of  the  slide  to  that  of  the  crank  arm  instead  of  referring 
it  to  the  piston,  as  is  more  usually  done.  While  it  is  more  natural  to  think 
of  the  position  of  the  valve  with  the  piston  at  half  stroke,  for  example, 
yet  when  we  reflect  that  this  piston  at  half  stroke  gives  two  positions  for 
the  valve  instead  of  one,  it  becomes  evident  that  to  define  the  position  of 
the  valve  as  that  due  a  certain  crank  angle,  90°  in  the  case  taken,  or  crank 
position  given  by  drawing  or  otherwise,  is  more  exact.  For  we  so  easily 
find,  by  drawing,  the  place  of  the  piston  or  cross-head  when  the  crank 
position  is  given,  or  the  reverse,  that  no  difficulty  will  be  met  with  in  our 
study  if  we  confine  ourselves  to  the  connection  between  crank  and  valve 
position,  in  place  of  the  more  usual  statement,  the  connection  between 
piston  and  valve  positions.  The  methods  used  are,  therefore,  those  of 
drawing,  and  little  computation  is  needed. 

The  position  of  the  valve  with  regard  to  its  eccentric  is  readily  found 
as  follows:  In  Fig.  3,  A  B  is  the  throw  of  the  eccentric,  F  C  the  crank, 
and  C  D  the  eccentric  radius;  D  being  the  centre  of  the  eccentric  while  C 


FIG.  3. 


18 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


is  the  centre  of  the  shaft.  To  find  the  position  of  the  valve,  draw  D  E 
from  E  perpendicular  to  A  B.  Then  will  C  E  be  the  distance  the  valve 
has  moved  from  its  middle  position,  and  E  B  and  E  A  the  distances  of  the 
valve  from  the  end  of  its  travel  in  either  direction.  By  combining  this 
with  C  F,  the  position  of  the  crank  arm,  we  see  that  we  have  the  angle 
between  the, crank  and  eccentric.  A  convenient  method  of  examining  the 
whole  motion  at  once,  is  found  to  be  by  laying  out  on  C  D  or  C  F  the  dis- 
tance CE=CCr=CH,  and  moving  the  point  G  or  H  as  the  shaft  is 
turned. 

We  will  take  a  position  of  Fig.  3  on  a  larger  scale  in  Fig.  4,  and  make 
the  construction  for  different  positions  by  laying  upon  the  eccentric  arm 
the  amount  the  valve  has  moved  from  the  centre  for  that  position  of  the 
eccentric.  In  doing  this  we  see  at  once  that  if  there  be  drawn  from  the 
point  A,  or  end  of  the  travel,  a  perpendicular  upon  the  eccentric  arm,  A  F, 
the  distance  C  E  —  C  F,  which  is  the  required  distance  from  the  middle 
position.  Make  C  Ff  on  the  crank  arm  =  C  .Fon'the  eccentric  arm.  By 


FIG.  4. 

drawing  these  for  different  positions  it  will  be  found  that  the  point  F 
always  falls  upon  one  of  two  circles  whose  centres  are  at  G  and  H,  one 
half  of  C  A  and  C  B  from  C.  This  may  be  verified  by  trial,  or  by  consid- 
ering that  A  F  C  is  always  a  right  angle  and  therefore  inscribed  in  a  semi- 
circle, since  C  A  is  common  to  all. 

The  point  Ff  will  always  lie  on  one  of  two  circles  having  the  same 


ON  VALVE  GEAR. 


19 


FIG.  5. 


radii  as  before,  but  with  centres  I  and  J,  which  lie  upon  a  line  I J  making 
an  angle  with  A  B  at  the  point  C,  where  it  intersects  it,  said  angle  I  C  A  = 
D  C  I",  the  angle  between  crank  and  eccentric;  for  when  the  crank  is  at 
1  C,  the  eccentric  is  at  C  A,  and  the  valve  is  therefore  farthest  from  the 
middle.  We  shall  call  the  circles  just  found  the  distance  circles,  for  by 
drawing  any  position  C  F'  of  the  crank,  we  find  that  the  valve  is  distant 
C  f  from  its  middle  position. 

We  are  now  in  a  condition  to  state  and  solve  our  first  problem: 
Given,  the  angle  between  the  crank  and  eccentric  arms  and  the  travel  of 
the  valve;  to  find  the  position  of  the  valve  for  any  position  of  the  crank. 

In  Fig.  5  lay  off  A  B,  the  full 
travel  of  the  valve,  and  bisect  A  B  in 
C.    Lay  off  D  C  A,  the  angle  between 
the  crank  and  eccentric  arms,  and 
make  D  C  =  i  A  C,  also  produce  D  C 
and  make   C  E  =  D   C.    Draw  two 
circles  from  D  and  E  as  centres  with 
radii  =  C  D»    These  are  the  distance 
circles.     For   any    position   of   the 
crank,  as  C  F  or  C  F' ,   or  C  F",  the 
amount  the  valve  has  moved  from  its 
,      middle  position  is 
given  by  the  dis- 
tance from  C  to  G, 
G',  or  G".    If  the 
crank  arm  cut  the 
circle  D  the  valve 
is  to  the  right  of 
the    centre,    if    it 
cut   the   circle  E, 
the  valve  is  to  the 
left  of  the  centre. 
If  a  rock  shaft 
is    used    between 


the  eccentric  rod  and  valve  rod,  as  usual  with  American  locomotives,  the 
same  diagram  can  be  used,  but  the  crank  arm  must  always  be  con- 
sidered as  if  it  were  on  the  other  side  of  the  shaft  from  that  which  it 
actually  is. 

Now  this  construction  is  not  any  better  than  the  one  given  before  in 
Fig.  3,  as  far  as  finding  any  one  relation,  or  the  position  of  valve  from  one 
given  crank  position;  but  it  is  more  comprehensive  and  we  can  easily  fol- 
low the  backward  and  forward  movement  of  the  valve  as  we  have  the 
rotating  motion  of  the  crank,  the  valve  always  moving  to  and  fro  on  its 
seat,  while  its  distance  from  the  centre  of  its  movement  is  seen  always  to 
be  the  amount  cut  off  on  the  crank  arm  by  the  distance  circle.  Figure  6 
shows  a  longitudinal  section  of  the  slide  valve  as  usually  constructed. 
When  placed  in  its  middle  position  it  completely  covers  the  cylinder  ports 


20 


STEAM  USING;  Oil,  STEAM  ENGINE  PRACTICE 


and  projects  beyond  them  on  both  sides.  The  name  given  to  the  exter- 
nal projection  is  lap,  or  steam  lap,  and  to  the  internal  projection,  exhaust 

lap.  These  names  are 
used  to  denote  the  linear 
amount  of  these  projec- 
tions  as  well  as  the  pro- 
jections themselves. 

It  is  evident  from  the 
FJG.  fi.  diagram  that  the  cylin- 

der port  at  one  end  can 

not  be  opened  to  the  steam  until  the  valve  shall  have  moved  away  from  that 
end  a  distance  equal  to  the  steam  lap;  nor  can  the  same  port  be  opened 
to  the  exhaust  until  the  valve  is  moved  from  the  centre  towards  the  port 
a  distance  at  least  equal  to  the  exhaust  lap;  and  if  we  lay  one  of  these  laps 
on  the  crank  arm  it  will  describe  with  them  two  circles  upon  the  centre 
C.  Introducing  this  element  into  our  diagram  we  are  ready  to'answer  our 
next  problem: 

During  what  portion  of  the  revolution  is  the  cylinder  open  to  the  steam 
and  to  the  exhaust,  the  angle  between  the  crank  and  eccentric  arms,  the 
travel,  and  the  laps  being  given? 

Lay  off  in  Fig.  7  the  full  travel  A  B  bisecting  in  C,  and  draw  the  line 
D  C  E  through  C,  making  the  angle  D  C  A  equal  to  the  angle  between 


FIG.  7. 

the  crank  and  eccentric  arms.  On  D  and  E,  as  centres,  draw  the  two  dis- 
tance circles  with  D  C  and  E  C  as  radii.  With  the  given  steam  and  ex- 
haust laps  as  radii,  draw  circles,  or  portions  of  circles,  on  C  as  a  centre, 


VALVE 


21 


cutting  the  distance  circles  in  eight  points.  Through  these  eight  points 
draw  radii  from  C.  When  the  valve  distance  is  greater  than  the  lap  circle, 
one  side  is  open  to  the  steam;  and  when  the  valve  distance  is  greater  than 
the  exhaust  lap,  one  side  is  open  to  the  exhaust.  When  the  valve  distance 
is  less  than  the  steam  lap,  the  steam  is  closed  at  one  end  and  the  exhaust 
at  the  other  end  is  open,  or  closed,  as  the  valve  distance  is  greater,  or 
less,  than  the  exhaust  lap. 

From  F  to  G  the  steam  is  open  at  the  left  end,  and  from  F'  to  (•?'  at  the 
right  end.  From  H  to  I  the  left  end  exhaust  is  opened,  and  from  H'  to  /' 
the  right  end.  For  an  engine  without  a  rock  shaft  the  cylinder  is  sup- 
posed to  be  at  the  right  of  the  diagram,  and  for  an  engine  with  a  rock  shaft 
the  cylinder  is  supposed  to  be  at  the  left.  The  rotation  is  from  D  to  A 
through  G. 

When  the  valve  has  moved  to  the  right  the  right  exhaust  and  left 
steam  ports  are  open.  When  the  valve  moves  to  the  left  the  left  end  opens 
to  the  exhaust  and  the  right  end  opens  to  the  steam.  The  valve  moves  to 
the  right,  if  there  be  no  rock  shaft,  when  the  crank  cuts  the  circle  D,  and 
to  the  left  when  it  cuts  the  circle  E.  With  a  rock  shaft  we  may  consider 
the  crank  arm  to  be  moved  180°  on  the  shaft  without  other  change  in  the 
diagram.  In  this  problem  there  are  various  points  involved.  First,  the 
angle  between  the  crank  and  eccentric  arms;  second,  the  travel  of  the 
valve;  third,  the  position  of  the  crank  when  the  steam  opens;  fourth,  the 
steam  lap;  fifth,  the  position  of  the  crank  when  the  exhaust  opens;  sixth, 
the  exhaust  lap;  and  we  can,  of  course,  with  all  these  data,  solve  other 
important  questions,  one  or  two  of  which  we  shall  introduce  and  con- 
struct. 

Given,  the  travel  and  position  of  crank  for  opening  and  closing  to  the 
steam;  to  find  the  angle  between  the  crank  and  eccentric  arms: 

In  Fig.  8  set  off  the 
trave  A  B  bisecting  at  C, 
and  through  C  draw  the 
<;  two  positions  of  the  crank 

when  the  ports  are  to 
open  and  close  to  the 
steam,  C  H  and  C  F  re- 
spectively. Bisect  the 
angle  H  C  F  by  the  line 
C  D.  Then  will  D  C  A 
be  the  required  angle 
between  the  crank  and 
eccentric  arms. 

Given,  the  travel  of 
the  valve,  angle  between 
crank  and  eccentric  and 
point  of  closing  to  steam,; 
to  find  the  lap. 
In  Fig.  8  set  off  A  B  equal  to  the  full  travel,  bisecting  in  C;  layoff  A  CD 


l> 


FIG.  8. 


22  STEAM  USIXH;  VK,  STEAM  ENGINE  PliA  <  'TI< 'K. 

equal  to  the  angle  between  the  crank  and  eccentric  arms;  draw  the  distance 
circle  from  Eas  a  centre  through  C  with  radius  0  J^equal  to  £  A  B,  and  draw 
C  F,  the  required  position  of  crank  at  point  of  cut  off.  C  G  is  the  steam 
lap,  for  where  C  F  cuts  the  distance  circle  the  valve  is  closing  the  steam 
port.  Drawing  the  arc  G  I  from  C  as  centre,  with  C  G  radius,  we  find  the 
steam  opens  at  C  I  a  little  before  the  crank  gets  to  the  dead  point.  The 
distance  J  Kis  the  amount  the  valve  is  open  at  the  end  of  the  stroke,  and 
the  opening,  and  amount  of  opening,  are  known  as  steam  lead.  If  this 
opening  be  thought  too  great  the  eccentric  must  be  moved  on  the  shaft 
and  the  lap  found  again  as  before.  As  D  C  always  bisects  H  C  F,  this  pre- 
sents no  difficulty.  And  it  is  to  be  remembered  that  D  J  is  always  at 
right  angles  to  A  B. 

Given,  the  travel,  lap  and  lead;  to  find  the  cut  off: 

Set  off  in  Fig.  8  the  full  travel  A  B  bisecting  at  C.  From  C  lay  off 
C  K  equal  to  the  lap,  and  make  K  J  equal  to  the  lead.  Draw  J  D  at  right 
angles  to  A  B,  and  make  C  D  equal  to  A  C,  equal  to  C  B,  by  taking  C  as  a 
centre  and  striking  an  arc  with  A  C  as  radius  cutting  the  perpendicular 
J  Din  D.  Bisect  C  D  in  E  and  draw  the  distance  circle  through  D  Jaud 
C,  using  E  C  as  radius.  Draw  also  the  arc  I  K  G  with  the  lap  C  K  as 
radius,  and  draw  C  F  through  G.  C  F  is  the  position  of  the  crank  at 
cutting  off  steam. 

A  little  practice  with  this  method,  first  upon  actual  valves,  and  then 
by  combining  the  foregoing  problems,  introducing  also  the  exhaust,  will 
soon  give  a  feeling  of  confidence  not  easily  obtained  with  the  usual 
methods. 

There  is  yet  one  case  with  a  common  slide  valve  which  it  is  desirable 
to  examine.  In  the  foregoing  examples  we  have  supposed  the  eccentric 
rod  to  be  nearly  parallel  to  the  line  joining  the  centre  of  the  shaft  and  the 
crosshead,  either  by  placing  the  steam  chest  on  the  side  of  the  cylinder,  or, 
if  it  be  on  the  top  of  the  cylinder,  by  the  use  of  rock. shafts.  Now  the 
latter  are  always  ugly,  and,  although  much  used,  the  former  arrangement 
is  to  be  preferred  when  possible.  There  are,  however,  cases  in  which  it  is 
convenient  to  lead  the  eccentric  rod  in  an  angle  to  the  line  from  the  shaft 
centre  to  the  crosshead,  the  steam  chest  being  on  top  of  the  cylinder  and 
the  valve  rod  jointed  and  guided;  or  else  the  steam  chest  is  at  one  side  of 
the  cylinder,  but  is  above  or  below  the  centre. 

The  action  of  an  oblique  connecting  rod  is  seldom  explained,  or  more 
rarely  fully  understood,  and  we  shall  therefore  devote  some  attention 
to  it.  Looking  at  the  general  case  in  Fig.  9,  we  see  that  the  further 
end  of  the  connecting  rod  can  come  no  nearer  the  shaft  than  the  differ- 
ence in  length  between  the  rod  and  crank,  and  can  go  no  further  from  the 
centre  of  the  shaft  than  the  sum  of  the  lengths  of  the  rod  and  crank,  and 
that  these  are  absolutely  the  only  limits  imposed  by  the  crank.  Thus,  in 
Fig  9,  by  taking  C  B  as  the  length  of  the  connecting  rod,  and  C  A  as  the 
length  of  the  crank,  by  drawing  from  C  as  a  centre  two  arcs  with  radii 
equal  to  A  C  +  C  B  and  C  B  -  A  C,  the  only  limit  to  the  stroke  is  that  its 
ends  shall  lie  on  these  lines  and  that  it  should  take  place  between  them. 


ox  VALVE  (;I-:MI. 


23 


The  path  of  the  outer  end  may  be  straight  or  curved.  For  slide  valves 
worked  in  this  manner  it  is  usually  straight,  the  end  moving  in  guides;  or 
nearly  straight  with  attachment  by  a  comparatively  long  link,  so  that  the  arc 
it  moves  in  is  flat  and  close  to  a  straight  line.  Suppose  it  is  straight,  then  it 
can  be  seen  that  the  length  of  the  stroke  produced  by  a  given  crank  may 
be  varied  considerably,  as,  for  example,  at  D  E  and  F  G,  the  latter  being 
plainly  the  greater.  Another  feature  is  also  introduced:  that  is,  that  for  a 
uniform  revolution  of  the  crank,  the  times  of  forward  and  backward 
strokes,  which  are  the  same  for  D  E,  are  not  equal  for  F  G,  because  the 


FIG.  9. 


dead  points,  which  always  occur  when  the  crank  and  rod  are  in  the  same 
line  with  each  other,  when  the  motion  changes,  are,  for  the  stroke  F  G,  at 
the  points  J  and  K.  These  are  not  on  the  same  diameter,  and  it  will  take 
longer  to  pass  from  J  to  K  and  F  to  G  than  K  to  J  and  G  to  F,  the  revolu- 
tion being  right-handed.  This  is  taken  advantage  of  as  a  "quick  return 
motion"  in  some  slotting  machines.  If,  now,  the  middle  of  the  stroke  F  G 
at  H  be  found,  and  the  straight  line  H  L  Ar  C  be  drawn,  the  dead  points  K 
and  J  will  not  lie  on  this  line  but  near  it,  and  the  longer  the  rod  is  com- 
pared with  the  crank,  and  the  smaller  the  angle  E  C  H,  the  closer  will  be 
the  agreement;  and  when  the  crank  is  on  this  line  the  other  end  of  the 
connecting  rod  will  be  close  to  the  points  F  or  G,  as  the  case  may  be. 
If  the  motion  were  studied  on  the  line  A  E  only,  being  a  parallel  to 
F  G  passing  through  C,  it  would  take  place  as  if  moved  by  a  crank  arm 
C  A  instead  of  C  L,  which  is  at  the  angle  ACL  from  the  other,  and,  in 
fact,  we  may  call  C  A  an  equivalent  crank  for  C  L,  for  it  will  cause  the 
stroke  D  E  to  be  made  at  the  same  time  as  C  L  moves  F  G,  the  rod  coming 
to  D  in  one  case  when  the  other  comes  to  F,  and  to  E  when  the  other 
arrives  at  G. 


24 


STEAM  T'SrXG;  Oh',  STEAM  ENGINE  P 7? AC 'TIC 'E. 


In  applying  the  valve  diagram  to  an  engine  of  this  kind,  the  only 
change  we  have  to  make  is,  that  instead  of  using  the  actual  angle  between 
the  crank  and  eccentric  arms,  we  must  use  in  its  place  the  angle  between 
the  crank  and  the  equivalent  eccentric  arm;  that  is,  it  must  be  changed  by 
the  angle  between  C  A  and  C  L,  or  A  C  L,  in  other  words,  by  the  angle  at 
the  centre  of  the  crank  shaft  between  the  lines  there  from  one  to  the 
centre  of  the  travel,  and  the  one  to  the  place  where  we  have  assumed  our 
investigation  to  be  made.  These  lines  may  also  be  said  to  pass  from  the 
centre  of  the  shaft  through  the  average  dead  points  and  the  other  through 
the  equivalent  dead  point.  This  change  will  be  an  increase  or  decrease 
in  the  angle  between  the  crank  and  eccentric  arms,  or  rather,  the  travel 
line  and  the  line  joining  the  centres  of  the  distance  circles,  according  as 
the  rotation  is  right  or  left-handed,  there  being  no  rock  shaft  used. 


FIG.  9A. 

Such  engines  are  not  very  common,  but  the  only  objection  lies  in  the 
necessity  of  guiding  the  end  of  the  valve  rod. 

In  the  preceding  paragraphs  we  have  discussed  the  case  of  an  eccen- 
tric fixed  on  the  shaft,  and  moving  a  single  slide  valve,  in  such  a  manner 
that  no  change  is  made  in  the  relation  or  movement  of  parts  while  the 
engine  is  in  motion,— all  adjustments  being  made  during  rest.  This 
also  may  be  taken  to  apply  to  the  old-fashioned  "D"  slide,  to  "B"  valve, 
and  to  piston  valve  engines,  and  these  types  are  in  most  general  use. 
The  advantages  of  simplicity,  durability  and  universal  acquaintance  are 


OJV*  VALVE  GEAR. 


found  to  outweigh  many  points,  even  the  waste  of  steam.  The  desire  to 
change  the  points  of  cut-off,  either  with  the  engine  stopped  or  in  motion, 
and  the  necessity  of  reversing  the  direction  of  rotation  in  many  engines, 
have  led  to  the  use  of  two  eccentrics  working  one  or  two  slide  valves,  and 
in  some  cases  to  three  eccentrics  working  two  slides.  The  necessity  of 
reversing  was  the  cause  of  the  adoption  of  two  eccentrics  before  any  change 
in  the  expansion  was  considered.  The  first  reversing  gear  used  with  the 
slide  valve  was  probably  some  form  of  hook  attachment  to  a  rock  shaft 
carrying  pins  on  both  sides  of  the  centre.  If  a  valve  be  made  without  lap 
or  lead  the  steam  follows  the  piston  full  stroke,  and  the  position  of  an 
eccentric  is  90°  in  advance  of  the  crank, — to  reverse  the  position  of  the 
eccentric  it  must  be  changed  180°. 


FIG.  9B. 

When,  however,  there  is  lap,  it  is  evident  that  there  can  not  be  an  equal 
opening  for  forward  and  for  back  gear  with  eccentric  arms  180°  apart;  but, 
as  we  have  already  stated,  the  eccentric  arm  is  more  than  90°  in  advance  of 
the  crank,  and  all  that  is  required  is  to  use  the  same  angle  between  the  crank 
and  eccentric  arms  for  each  motion.  Figs.  9  A  and  9  B  show  two  arrange- 
ments for  accomplishing  this  with  a  single  eccentric.  The  eccentric  is  not 
keyed  to  the  shaft,  but  is  bolted  to  the  face  of  a  disc  of  smaller  diameter, 
rigidly  fastened  to  the  shaft.  In  one  of  the  arrangements  shown,  the 
eccentric  can  move  freely  about  one  of  the  bolts  as  a  centre,  while  the 
other  projects  through  a  curved  slot.  This  second  bolt  can  either  be 
tightened,  holding  the  eccentric  to  the  disc  in  rny  position  between  the 


26 


STEAM  rsi.\(,:   (>/,',  STEAM  ENGINE  PRACTICE. 


2    C8 
+a    O  .W 


(*!{ 

sii 

I  a  -2  i 


.  .2 


rQ      CD      CD 

fl  «  .2  p 


«  0  *  S 

-O-'S 

<u    o    Q   a> 

1.2^ 


o  g  a  « 
.2  'C  *  B 


11 


ON  VAL  VE  GEAR.  27 


two  extreme  ones,  thus  allowing  a  change  in  the  eccentric  arm  when  the 
engine  is  still;  or,  the  engine  being  moved  till  the  eccentric  comes  to  rest, 
with  the  end  of  the  slot  against  the  bolt,  of  course  the  eccentric  will 
follow  the  motion  of  the  shaft,  and  the  crank  and  slot  being  properly 
arranged,  the  valve  will  keep  the  engine  running  in  the  direction  in  which 
it  was  started.  If,  on  stopping,  the  engine  be  moved  by  hand  so  as  to  run 
in  the  other  direction,  the  shaft  and  disc  will  move  until  the  eccentric 
is  caught  up  with,  and  the  engine  will  drag  it  properly  to  continue  the 
motion.  It  is  therefore  a  simple  reversing  gear  for  engines  small  enough 
to  be  easily  turned  by  hand.  Sometimes  a  small  fly-wheel  has  been 
mounted  with  the  eccentric  and  a  quick  closing  valve  placed  on  the  steam 
pipe.  By  closing  the  steam  valve  quickly  the  fly-wheel  will  carry  the 
eccentric  round  so  that  the  engine  would  start  in  the  other  direction;  while 
011  the  other  hand,  if  the  steam  valve  be  closed  slowly  the  eccentric  will 
remain  in  contact  with  the  disc  and  the  engine  will  start  in  the  direction 
it  had  been  moving— an  arrangement  hardly  promising  to  remain  long  in 
working  order.  In  larger  engines  the  same  curved  slot,  or  the  straight 
slot  shown  in  the  other  figure,  9  B,  is  used,  and  the  eccentric  is  traversed 
by  a  sleeve  and  key;  the  latter  is  spiral  and  is  so  arranged  that  by  moving 
the  sleeve  along  the  shaft  the  eccentric  is  shifted  across  the  shaft.  The 
movement  of  the  sleeve  is  effected  by  a  yoked  lever. 

The  construction  of  the  valve  diagram  for  different  positions  of  these 
eccentrics,  and  the  change  in  the  cut-off  produced  thereby,  is  a  very 
desirable  study  for  the  student.  Where  two  eccentrics  are  used  for  moving 
a  slide  valve  they  are  usually  fastened  to  the  shaft,  and  the  rods  are 
attached  to  the  eccentric  by  straps  or  yokes;  the  other  ends  of  the  rods 
are  connected  by  pins  to  a  piece  called  the  link.  There  are  three 
varieties  of  the  motion  which  goes  under  the  name  of  link  motion,  but 
of  late  years  one  or  both  of  the  eccentrics  have  been  omitted  and  the 
link  moved  from  some  other  portion  of  the  moving  mechanism.  The 
three  kinds  noted  have  been  long  in  use,  and  are  known  as  the  shift- 
ing link,  being  the  invention  of  Howe,  a  foreman  in  Stephenson's 
Locomotive  Works,  or  the  Stephenson  Link,  the  Gooch,  or  Fixed  Link, 
produced  about  the  same  time  in  the  locomotive  shops  of  Mr.  Daniel 
Gooch.  and  the  straight  link  of  Alexander  Allan,  a  combination  of  the 
other  two. 

Fig.  10  shows  clearly  the  arrangement  for  the  shifting  link  in  its  most 
simple  form.  The  link  joining  the  ends  of  the  two  eccentric  rods  is  slot- 
ted out  and  the  valve  rod  is  pinned  to  a  rectangular  block,  sliding  in  the 
slot,  but  which  in  this  simple  form  can  be  clamped  to  the  link.  When 
loose,  the  link  can  be  moved  by  the  handle  at  its  end  until  it  occupies  any 
given  or  desired  position.  It  will  be  seen  that  if  the  link  be  placed  with 
one  end  of  the  slot  against  the  slider,  the  valve  will  move  by  the  eccentric 
connected  to  that  end  of  the  link  almost  entirely,  and  we  shall  have  to  ex- 
amine the  motion  when  the  slider  is  clamped  at  some  intermediate  point 
between  the  ends.  In  order  that  the  centre  of  the  valve  may  remain 
unchanged  for  all  positions  of  the  link,  a  curvature  must  be  produced  in 


28 


STEAM 


07?,  STEAM  ENGINE  PRACTICE. 


the  slot;  otherwise,  as  the  link  is  moved,  say  from  its  end  to  the  centre, 
the  valve  is  pulled  over  toward  the  shaft.  The  valve  still  has  the  same 
motion  as  a  whole,  its  travel  is  simply  displaced,  thereby  producing 
unequal  distribution  of  the  steam  to  each  end  of  the  cylinder.  By  curv- 


FIG.  10. 

ing  the  link  to  an  arc  with  a  radius  equal  to  the  distance  from  the  centre 
of  the  shaft  to  the  centre  of  the  slider  when  the  valve  is  placed  in  its  cen- 
tral position  on  its  seat,  this  action  is  removed. 

In  Figure  11,  for  the  sake  of  clearness,  consider  the  link  as  a  straight 
bar,  the  extremities  of  which  are  hung  in  such  a  manner  that  the  ends  L 
and  L'  can  only  move  in  lines  nearly  parallel  to  the  line  A  C  B;  this  may 
be  the  case  exactly  for  either,  or  nearly,  for  one  or  both  of  the  points 
L  L' '.  Inasmuch  as  C  L  and  C  L'  both  make  angles  with  C  A,  both  ends 


FIG.  11. 


of  the  link  may  come  under  the  case  of  oblique  eccentric  rods.  But 
this  presents  no  great  difficulty.  If  the  link  were  moved  till  L  came  to 
the  slider  M,  the  motion  received  by  the  valve  would  be  that  due  to  the 


OX  VALVE  GEAR. 


29 


eccentric  E;  but  for  the  given  position,  the  point  L  receives  motion 
parallel  to  A  C  as  if  it  were  driven  by  a  virtual  eccentric  at  F,  with  angle 
between  crank  and  virtual  eccentric  arm,  A  C  F  equal  to  L  C  E,  Avhile  the 
point  L'  receives  motion  from  E',  as  if  moved  by  a  virtual  eccentric  at  E*, 
with  the  angle  A  C  ^  equal  to  the  angle  L,'  C  EJ ' .  In  general 

A  CF+  A  CFf  =  L  CE+  L'  C  F/ . 

E  C  F/-(A  C  F  +  A  C  F')  =  ECF/  —(L  C  E  +  L'  C  E^); 
or,  EC  F+  F/  CF-  =  A  CL  +  A  C  L'  =  L  C  L'  =  the  link  angle. 
Hence,  also,  the  angle,  F  C  F' ,  between  the  virtual  eccentric  centres  is 
constant,  and  it  swings  around  its  vertex  C  as  the  link  moves.  If  the  link 
be  divided  in  any  proportion,  the  link  angle  should  be  divided  in  the  same 
proportion ;  and  an  angle  may  be  set  proportionately  to  the  number  in 
which  L  M  divides  L  L' .  L  and  L'  then  move  exactly  as  if  they  were 
on  the  line  C  A  driven  by  the  virtual  eccentrics,  F  and  F' ;  for  E  comes 
to  its  dead  points  when  F  comes  to  C  A,  and  I?",  when  F  comes  to  C  A, 
the  dead  points  for  E  and  F  being  on,  or  very  near  the  lines  C  L  and 
C  Li'  respectively. 

We  have  now  to  examine  the  motion  of  a  point  on  a  bar,  when  the 
bar  is  moved  at  two  points,  as  if  connected  with  a  crank  or  eccentric 
at  each  of  such  points.  We  have  established  for  the  points  of  connection 
L  and  L',  the  virtual  eccentrics  from  which  they  receive  motion,  as  far  as 
the  line  A  C  is  concerned,  and  we  come  to  the  motion  of  the  point  M,  as 
follows: 

The  motion  of  M  may  be  found  by  considering  that,  if  Lf  were  fixed 
while  L  moves,  the  motion  of  M  would  be  definite;  and,  also,  if  L  were 
fixed  while  L'  moves,  the  motion  of  M  would  again  be  definite;  while  if 
L  and  Lf  both  move,  the  point  3/  would  have  a  motion  equal  to  the 

resultant  of  these  two  motions. 
Now,  enlarging  a  part  of  our  Fig. 
11,  we  see  in  Figs.  11  and  12,  using 
the  virtual  eccentrics  F  and  F*, 
as  it  has  been  shown  we  must  do, 
that  if  Lf  be  fixed,  F/  Lf  discon- 
nected, and  C  K  be  made  the  same 
A  part  of  C  F  that  L'  M  is  of  LL', 

the  point  M  will  move  as  if  driven 
by  an  eccentric  with  centre  at  K 
and  a  rod  at  M  K;  and  also  that  if 
L  be  fixed  while  'E  L  is  discon- 
nected, and  C  Kf  be  made  the 
same  part  of  C  Ff  that  L  M  is  of 
L  L',  the  motion  of  M  will  be  as  if 
derived  from  a  single  eccentric, 
centre  at  K',  by  a  rod  K'  ^f.  To  combine  these  two  motions  at  once, 
draw  K  N  equal  and  parallel  to  C  K' ;  then  does  the  point  A"  revolve 
about  A"  as  K'  does  about  (\  And  also  draw  K'  N  equal  and  parallel  to 
C  K\  then  does  the  point  N  revolve  about  Kf  as  K  does  about  C.  Either 


FIG.  12. 


3O 


STEAM  USING;  OR.  STEAM  ENGINE  PRACTICE. 


way  we  look  at  it  N  revolves  about  K  while  K  revolves  about  C;  or  N 
revolves  about  Kf  while  K'  revolves  auout  O,  and  hence  the  point  M 
moves  as  if  directly  connected  with  the  point  N  by  a  rod  M  N  of  fixed 
length.  The  point  ^Yrnay  therefore  be  called  the  virtual  eccentric  centre, 
and  C  N  the  virtual  eccentric  arm,  for  the  point  M.  It  is  also  seen  that 
the  point  Nis  on  the  line  F  Ff ',  which  it  divides  in  the  proportion  that  M 
divides  L  L' ;  for  the  triangles  F  K  N,  N  K'  Ff  and  F  C  F' ,  are  all  similar, 
and  the  line  F  F'  may  be  drawn  and  the  point  N  found  at  once  by  making 
Ff  N  the  same  part  ofFF*  that  ML  is  of  L  I/.  This  is  a  more  conven- 
ient construction  for  the  point  N  than  the  other,  which  was,  however,  only 
intended  for  demonstration.  It  may  be  necessary  again  to  caution  the 
reader  that  the  components  of  motions  are  all  understood  to  be  parallel 
to  A  O. 

If  the  link  was,  as  a  whole,  fixed,  or  was  not  to  be  changed,  we  could 
find  once  for  all  the  virtual  eccentric  for  the  end  points  L  and  L' ,  and 
draw  FFf  at  once.  But,  as  in  the  shifting  link  motion,  we  use  all  portions 
of  the  link  which  is  moved  about  C  A,  we  have  F  coinciding  with  E  when 
L  coincides  with  M,  and  then  N  falls  on  E.  As  the  link  is  moved  the  tri- 
angle F  C  Ff  is  swung  about  C,  and  the  point  N  travels  along  F  F'  till 
the  other  end,  L' ',  of  the  link  is  brought  to  ilf  when  the  point  N  reaches 
F'  which  coincides  with  Ef .  The  line  which  includes  all  positions  of  the 
point  N  is  a  kind  of  spiral,  but  is  approximated  by  Kankine  to  a  circle, 
and  by  Zeuner,  to  whom  the  whole  method  is  due,  to  a  parabola.  We 
will  content  ourselves  with  drawing  this  curve  as  the  arc  of  a  circle,  and 
with  finding  a  third  point  thereon  by  which  it  may  be  constructed.  We 
have  already  found  F  and  F/  on  this  curve  coinciding  vriih.' E  and  E' 
respectively;  then  if,  as  is  usually  the  case,  C  F  -  C  E,  the  middle  point 
of  the  curve  between  F  and  F'  is  easily  found.  Set  off  in  Fig.  13  the 
angles  E  C  F,  Ef  C  F' ,  each  equal  to  one-half  the  link  angle,  L  C  L',  then 
the  point  found  by  the  intersection  of  F  Ff  with  A  C  is,  for  this  case,  the 
middle  point  of  the  arc  E  N  E'  desired,  and  a  circle  is  passed  through 


FIG.  13. 


ON  VALVE 


31 


these  three  points.  If  the  link  be  drawn  in  mid-gear  and  we  take  the 
intersection  of  the  rods  L  E,  L'  E',  combining  this  with  our  valve  dia- 
gram, we  find  a  complete  mastery  over  the  link  motion,  and  we  will  try  to 
solve  some  of  the  cases  which  are  of  frequent  occurrence. 

Given,  the  full  travel,  the  laps  and  the  lead  in  full  gear  and  the  link 
angle;  to  flnd  the  mid  gear  travel  and  lead,  and  also  the  travel  and  lead  with 

points  of  admission,  cut  off,  compression  and 
release  for  any  given  position  of  the  link. 

Set  off,  in  Fig.  14,  C  L  =  the  lap  and 
L  P, equal  the  full  gear  lead;  from  C  as  a 
centre  swing  with  a  radius  =  one-half  the 
full  travel,  the  arc  E  F,  and  erect  the  per- 
pendicular P  E  cutting  this  arc  in  E.  Lay 
off  E  C  F  one-half  the  link  angle,  or  one- 
half  the  angle  between  the  end  radii  of  the 
link  itself  (which  is  not  shown  in  the 
figure),  and  drop  F  Q  perpendicular  to 
C  L.  Then  C  Q  is  one-half  the  mid-gear 
travel,  and  L  Q  is  the  mid-gear  lead.  By 
producing  E  P  to  E'  making  P  E'  =  P  E 
and  drawing  an  arc  through  E  Q  E' ,  we 
have  the  curve  on  which  the  single  virtual 
eccentrics  are  found.  Suppose  we  wish  to 
find  the  steam  and  exhaust  openings  and 
closings  for  that  position  of  the  link  which 
is  three- eighths  of  the  way  from  full  for- 
ward to  full  backward  gear.  Divide  the  arc 
E  E"  by  G,  so  that  E  G  is  three-eighths  of 
E  E'  measured  on  the  arc.  Join  C  G.  This 
is  one -half  the  valve  travel  required;  from 
the  middle  point  K  of  C  G  as  a  centre,  draw 
a  circle  with  radius  C  K;  and  from  C  as  a 
centre,  draw  the  lap  circles  or  portions  of 
them;  that  is,  the  radius  C  L  =  the  steam 
lap,  and  C  V=  the  exhaust  lap;  and  where 
these  arcs  cut  the  distance  circle  from  A", 
the  points  of  intersection  give,  by  drawing 
lines  from  C,  the  positions  of  the  crank 

C  S  f  or  steam  admission.  C  T  for  cut-off,  0  C  produced  for  release,  and 
V  C  produced  for  compression. 

It  sometimes  happens  that  the  forward  eccentric  is  the  lower  one  when 
we  make  our  examination,  and  in  such  a  case  we  must  lay  —  on  the  other 

side  of  C  E  and  C  E'  to  find  the  virtual  eccentric  centres  Fand  Ff ;  making 
the  necessary  construction  we  have  the  middle  point  of  the  line  F  F^,  or 
N,  as  the  single  virtual  eccentric  which  drives  the  block  in  mid-link,  and 
we  may  pass  our  curve  through  E,  E'  and  this  point  as  we  did  before;  but 


32 


OX  VALVE  GEAR. 


33 


we  find  it  curved  in  the  other  direction,  and  the  mid-gear  lead  is  less  than 
the  full  gear  lead,  while  in  the  first  case  it  was  greater. 


FIG.  15. 

The  fixed  link,  or  Gooch's  link-motion,  is  shown  on  page  32.  A  swing- 
ing rod  called  radius  rod  is  attached  to  the  valve  stem  and  carries  the  slider 
at  its  free  end.  This  rod  is  controlled  from  the  foot  board  in  the  same 
way  as  the  link  in  Stephenson's  motion,  and  the  actual  eccentric  centres 

are  the  virtual  eccentrics.  As 
the  eccentric  rods  do  not  change 
their  mean  angle  with  the  mo- 
tion line  the  single  virtual  ec- 
centric is  found  on  the  straight 
line  E&,  Figs.  13  and  15,  join- 
ing the  real  eccentric  centres, 
and  the  lead  does  not  change  for 
any  position  of  slider.  This  gear 
is  a  favorite  in  England,  but  is 
rarely  seen  in  the  United  States. 
In  Fig.  16  the  lap  and  valve 
circles  are  drawn  for  different 
gears  and  will  be  readily  un- 
derstood. 

The  difficulty  experienced 
in  fitting  the  curved  links  for 
the  shifting  and  fixed  link-mo- 
tions, and  the  fact  that  the  cur- 
vature in  the  link,  required  to 
keep  the  valve  at  the  same  place 
in  mid- travel,  was  in  different 
directions,  led  Mr.  Alexander 
Allan,  then  employed  at  the  Crewe  shops,  to  design  a  link,  shown  on  page 
32,  in  which  the  radius  rod  was  retained,  although  the  link  was  also  shifted; 


34  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

and  by  proper  proportions  of  the  rocker  arms,  attached  to  link,  and  of 
radius  rod,  a  straight  link  was  secured.  Of  course  these  straight  links 
were  easier  to  fit  than  the  curved  ones.  They  are  in  quite  general  use  in 
England  and  on  the  Continent,  while  in  the  United  States  they  have  been 
rarely,  if  at  all,  used. 

In  studying  this  link-motion  we  call  the  angle  from  the  centre  of  shaft 
through  which  the  link  is  shifted  a,  and  set  off  one-half  of  it  from  the 
actual  eccentric  centres  to  find  the  position  of  the  virtual  forward  and 
backward  eccentric  centres  for  mid-gear;  and  we  then  find  the  curve  on 
which  all  our  single  virtual  eccentric  centres  lie  as  in  the  case  of  the 
Stephenson  link.  The  curve  in  this  case  is  flatter,  and  the  change  from 
full  to  mid- gear  lead  is  less  than  for  the  Stephenson  link.  The  mid-gear 
lead  may  be  greater  or  less  than  full  gear  lead  according  as  the  upper  or 
lower  eccentric  is  used  for  forward  gear. 

No  drawing  is  required.  The  change  of  cut-off  for  different  positions 
of  the  slider  is  shown  by  the  distance  and  lap  circles  as  already  explained 
for  the  Stephenson  and  the  Gooch  links. 

The  rock  shaft  arms  have  to  be  proportioned  to  the  segments  into 
which  the  line  from  centre  of  shaft  to  centre  about  which  radius  rod 
vibrates  is  divided  by  the  vertical  through  the  centre  of  rock  shaft. 

All  three  of  the  gears  described  as  having  two  eccentrics  are  used  for 
reversing  gears  as  well  as  for  changing  point  of  cut-off;  and,  in  fact,  were 
used  only  for  the  former  purpose  years  before  their  value  for  the  latter  was 
appreciated.  For  many  years  these  three  were  the  only  forms  employed. 
Of  late  years,  however,  a  variety  of  gears  for  varying  point  of  cut-off  and 
for  reversing  the  motion  of  the  engine  have  come  into  use,  which  we  will 
discuss  in  order  of  complexity  rather  than  of  age. 

One  of  the  most  widely  extended  modifications  of  the  link-motion  with 
two  eccentrics  is  met  with  in  the  valve  gear  of  Walschaert,  or  the  Heusin- 
ger  von  Waldegg  link-motion,  shown  on  page  35. 

In  the  ordinary  form  of  link-motion  we  have  two  eccentrics  attached 
to  two  points  on  the  link,  and  we  get  'more  or  less  of  the  motion  of  one 
eccentric  by  connecting  the  valve  rod  to  different  points  upon  the  link. 
Suppose,  however,  that  while  one  eccentric  attached  to  the  combination 
arm  remains  constant  as  to  length  of  its  arm  and  the  angle  it  makes  with 
crank  arm,  we  have  the  means  of  varying  the  length  of  the  other  eccentric 
arm,  which  is  attached  to  a  second  point  on  the  combination  arm  as  shown 
in  illustration.  If,  now,  the  valve  stem  be  connected  with  a  third  point  on 
the  combination  arm  the  movement  of  the  valve  can  be  controlled  by 
giving  more  or  less  travel  to  the  variable  arm,  and  can  be  reversed  by 
reversing  the  motion  of  this  arm. 

In  the  Walschaert  gear,  the  link,  or  combination  arm,  is  moved  by 
an  attachment  rod  from  the  cross- head,  and  its  lowest  point  moves  with 
the  piston  or  main  crank.  This  combination  arm  is  attached  at  the  upper 
end  to  the  valve  stem,  and  just  below  this  attachment  it  is  pivoted  to  a 
centre.  If  this  centre  were  fixed  the  valve  would  receive  only  the  motion 
due  to  a  virtual  eccentric  in  line  with  the  crank,  and  with  an  arm  which 


ON  VALVE  VEAK. 


35 


§ 

o: 
LU 
O 

C/5 

D 
UJ 

I 

LJ 

I 
h 

CC 

O 

cr 

LU 
< 

1 

LU 

I 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


bears  to  the  crank  length  the  fraction  that  the  short  distance  from  valve 
stem  to  pivot  is  of  the  length  from  pivot  to  pin  at  cross-head  connection. 
The  other  element  of  the  motion  is  obtained  by  connecting  the  pivot  of 
this  lever  to  a  vibrating  slotted  link,  pivotted  at  its  centre,  by  means  of  a 
rod  attaching  to  a  slider  in  the  link.  The  vibration  of  this  link  is  given 
by  a  small  eccentric  set  at  right  angles  to  the  crank,  or  by  a  return  crank 
from  the  main  crank  pin.  The  effect  of  moving  this  slider  in  the  vibra- 
ting link  is  to  change  the  travel  of  the  pivot  in  magnitude,  or  to  reverse 
its  motion;  the  pivot  always  reaches  the  end  of  the  stroke  and  its  centre 
at  the  same  part  of  the  revolution:  i.  e.,  its  period  of  vibration,  or  motion 
with  respect  to  the  motion  of  crank  remains  unchanged,  however  much 
the  radius  rod  may  be  changed;  but  the  amount  of  movement  received  by 
the  valve  stem  is  greater  than  that  received  by  the  pivot  in  the  ratio  of 
the  whole  length  of  the  combination  arm  to  the  portion  between  the  pivot 
and  cross-head  connection  pin. 

To  illustrate:     Suppose  the  stroke  of  the  piston  is  24  inches,  while  the 
combination  arm  is  26  inches,  with  the  pivot  2  inches  from  the  valve 

stem  connection.  The 
amount  which  the  valve 
moves  due  to  the  pis- 
ton movement  only,  is 
24(26-24) 


^ 

nearly,  not  exactly,  a 
slight  error  being  intro- 
duced by  the  connecting 
bar  from  the  cross-head 
to  the  link,  which,  in 
changing  its  inclination, 
reduces  the  travel  near 
the  ends  where  inclined 
to  the  stroke. 

If  the  radius  of  the 
eccentric  or  return  crank 
be  2  inches,  and  the  ex- 
treme length  of  the  vi- 
brating link  be  6  inches, 
3  above  and  3  below  the 
centre,  and  the  attach- 
ment of  the  vibrating  link 
to  eccentric  is  at  2  inches 
from  the  centre  of  the  vi- 
brating link,  we  can  easily 
draw  valve  diagram.  In  Fig.  17,  set  off  horizontally  1  inch,  which  equals  lap 

0/» 

+  lead,  from  the  centre  C  on  line  A  C,  and  then  vertically  a  distance  —     • 
the  distance  the  slider  is  from  the  centre  of  the  vibrating  link  =  2^  inches; 


FIG. 


ON  VALVE  <;EAR. 


37 


joining  this  point  with  C  we  use  this  line  as  the  diameter  of  the  valve  circle, 
and  by  drawing  the  lap  circles  we  have  all  the  points  as  before  for  the 
opening  and  closing  of  the  steam  ports.  This  gear  has  been  used  in  Europe, 
and  was  introduced  into  this  country  by  the  late  William  Mason,  who 
placed  it  on  many  of  the  light  engines  used  for  passenger  travel  at  Coney 
Island  beach  and  about  New  York. 

In  designing  the  preceding  forms  of  valve  gear,  many  little  points 
arise  with  regard  to  equalizing  quantity  of  steam  used  at  each  end  of  the 
cylinder,  and  for  so  arranging  the  details  that  the  wear  shall  be  a  mini- 


FIG.  18. 


mum.  A  detailed  study  must  be  made  in  each  case,  while  for  many  practi- 
cal points  the  works  on  "Link  and  Valve  Motions"  by  Zeuner,  and  also  by 
Auchincloss,  will  be  found  of  great  service. 

If  in  Fig.  18  we  compel  the  end  of  the  eccentric  rod  to  move  in  the  path 
H  K  we  know  that  the  end  of  the  rod  will  always  reach  the  centre  and  ends 


i-: . 


FIG.  18  A. 


38 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


of  the  travel  in  defined  time,  while  with  regard  to  a  motion  at  right  angles 
thereto  in  this  case  the  end  will  have  none.  Now,  if  the  path  is  from  F  to 
G,  it  can  be  seen  that  the  end  of  the  rod  has  a  very  respectable  component 
vertically,  but  that  it  reaches  the  end  and  centre  of  the  travel  at  the  same 
time  as  before,  or  nearly  so,  and  the  horizontal  travel  is  H  K  nearly,  and 
the  vertical  is  FH  +  KG.  By  changing  the  angle  of  the  path  we  find  the 
magnitude  of  the  path  may  be  changed  and  even  the  motion  reversed,  as 
F  passes  C  K,  and  at  the  same  time  the  vertical  motion  of  the  rod  at  the 
end  may  be  increased  or  diminished.  We  have  then  all  the  elements  for  a 
link  in  the  eccentric  rod  itself.  One  end  moves  up  and  down  with  the 
motion  of  the  eccentric,  and  the  other  end  moves  up  and  down  with  the 
in  and  out  motion  and  the  eccentric  rod  becomes  the  link. 

We  can,  of  course,  connect  the  valve  stem  to  a  slider,  leaving  the  path 


FIG.  19.  FIG.  19  A. 

MARSHALL'S  GEAR  FOR  MARINE  ENGINES. 


ON  VALVE  GEAR. 


39 


at  the  outer  end  fixed,  or  we  can  [connect  the  valve  stem  to  any  point  on 
the  link,  as  F,  and  change  the  angle  of  the  path  at  the  end,  thus  causing 
the  travel  to.\vary;  the  time,  however,  of  the  outer  end  up  and  down 
motion  being  the  same  as  that  of  the  in  and  out  motion.  The  valve  stem, 
of  course,  in  this  figure  moves  vertically. 

This  form  has  been  adopted  by  Mr.  F.  Marshall  for  moving  the  valves 
of  vertical  marine  engines.  The  arrangement  is  shown  in  Figs.  19,  19  A, 
and  19  B.j^In  Fig.  19,  the  form  of  path  adopted  for  the  outer  end  is  the 
arc  of  a  circle,^the  end  of  the  eccentric  rod  beiDg  connected  by  a  radius 


FIG.  19  B. 
MARSHALL'S  VALVE  MOTION  ENLARGED. 


rod  swung  from  the  point  0.  The  form  may  be  either  a  slot  or  the  arc  of 
a  circle.  Fig.  ISA  shows  a  straight  slot  in  the  face  of  a  disc  attached  to 
the  end  of  shaft  connected  with  a  reverse  lever. 

In  Fig.  19,  C  is  centre  of  shaft;  A,  crank  pin;  A  D,  connecting  rod;  E, 
centre  of  eccentric;  E  I,  link;  V.  valve  stem  connection;  O  L,  arm  fixed  to 
axis  of  geared  arc  Z  Z^  at  L;  W,  handwheel  which  moves  the  geared  arc 
by  means  of  worm  w;  O  7,  radius  rod  which  controls  movement  of  end  of 
link,  or  eccentric  rod. 


40 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


Mr.  Charles  Brown,  of  Winterthur,  Switzerland,  introduced  many 
varieties  of  this  form,  see  Fig.  20.  In  most  of  them  the  eccentric  was 
dispensed  with,  and  the  link  attached  to  the  connecting  rod  in  such  a 
manner  that  while  the  movement  in  the  direction  of  the  inclination 
is  reduced,  as  in  the  Walschaert  gear,  the  other  component,  that  due 
the  transverse  vibration  of  the  rod,  is  the  one  which  is  governed  by 
the  path  used. 

Mr.  Brown  usually  employed  some  form  of  parallel  motion  at  the 
outer  end  in  place  of  the  slotted  guide.  Most  of  his  work  was  applied 
to  engines  with  rods  quite  long  in  comparison  with  the  movements 
taken  from  them,  and  both  Marshall  and  Brown  attached  the  valve 
stem  either  between  the  eccentric  and  guide,  or  outside  of  it  as  de- 
sired. 


A* 

FIG.  19C. 
DIAGRAM  FOB  MARSHALL'S  VALVE  GEAK. 

Mr.  David  Joy  has  introduced,  quite  extensively,  a  form  of  gear 
similar  to  Brown's  in  some  respects,  but  more  carefully  worked  out  in 
others;  Figs.  21  and  21  A.  Mr.  Joy  attaches  to  a  point  near  the  centre 
of  the  connecting  rod  a  bar  H  I;  Fig.  21  A.  This  bar  is  carried  by  a 
hanger  from  J,  a  fixed  point  in  the  frame  of  the  engine.  Now,  as  the 


ON  VALVE  GEAR. 


41 


FIG.  20. 
BROWN'S  VALVE  GEAR. 


FIG.  21. 

JOY'S  VALVE  GEAR  ON  A 
MARINE  ENGINE. 


cross-head  moves  from  D  to  E  the  point 
/  moves  in  the  arc  of  a  circle,  but  because 
the  length  H  I  is  short  it  gets  an  extra 
pull  in  when  the  cross- head  nears  the 
end  of  the  stroke.  Mr.  Joy  therefore 
carries  his  link  from  K,  a  point  on  H  I, 
to  the  guides  L,  and  attaches  the  valve 
stem  M  N  to  a  point  in  K  L,  in  this  case 
produced,  at  M.  The  results  have  been 
very  good,  and  in  most  cases  pin  joints 
are  used  for  eccentric  straps.  In  many 
cases  Mr.  Joy  replaces  the  guide  L, 
which  he  makes  curved  to  radius  de- 
pending on  N  M,  by  a  swinging  link 
having  the  same  centre  as  the  guide; 
this  centre  is  mounted  on  an  arm  of 
a  rock  shaft,  and  the  rock  shaft  cen- 
tre coincides  with  that  of  the  guide. 
Two  more  pin-joints  are  required  but 
the  wear  on  the  guide  is  removed. 

Mr.  Kirk  has  patented  a  form  of 
valve  gear.  In  a  marine  engine  he 
places  a  vibrating  link  on  the  air  pump 
side  levers  in  such  a  a  manner  that  the 
centre  of  the  link  is  moved  thereby 
from  the  piston  rod.  The  link  is  caused 
to  vibrate  by  the  transverse  motion  of 
the  connecting  rod  and  a  compensation 
due  the  obliquity  is  introduced.  In  this 
case  the  levers  adopted  are  in  the 


42 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


form  of  a  Watt  parallel  mo- 
tion. 

The  motion  used  for  a 
link  in  the  Allen  engine  for 
driving  a  slide  valve,  and  in 
the  Porter- Allen  for  moving 
the  steam  valves,  is  exceed- 
ingly elegant  and  clearly  set 
forth  in  Fig.  22.  The  link  is 
part  of  the  eccentric  strap, 
and  the  centre  of  the  link,  of 
which  only  one-half  is  con- 
structed for  non-reversing 
engines,  is  guided,  in  an  ap- 
proximately straight  line, 
by  a  swinging  rod  attached 
to  the  frame;  so  that  the 
small  versed  sine  of  half 
the  arc  of  swing  is  bisected 
by  the  centre  line  of  engine 
and  the  chord  of  the  arc  is 
parallel  to  it.  The  eccen- 
tric is  forged  on  the  shaft 
and  corresponds  in  Fig.  23 
to  the  virtual  arm  A  B.  As 
we  proceed  up  the  link  we 
find  it  also  acting  as  a  bell 
crank,  and  we  see  that  by 
coming  up  the  vertical  B  to 
G  and  making  B  G  propor- 
tional to  distance  of  slider 
above  centre  line,  we  have 
the  virtual  eccentric  and 
distance  circle  for  any  point 
on  the  link. 

To  draw  the  valve  dia- 
gram for  any  point  on  the 
link,  lay  off  first  the  real 
eccentric  radius  on  the 
motion  line,  and  then  from 
that  point  lay  off  at  right 
angles  to  the  motion  line  a 
distance  equal  to  the  real 
eccentric  radius  multiplied 
by  the  ratio  of  the  distance 
of  the  slider  above  centre 
line  to  the  distance  from 


FIG.  21  A. 
JOY'S  VALVE  GEAK  ENLARGED. 


ON  VALVE  GEAR. 


43 


FIG.  22. 


centre  of  eccentric  to  the  point  of  attachment  of  rocker  arm.  The  point 
thus  found  is  the  virtual  eccentric  centre  moving  the  valve.  The  link  is 
of  course  curved  to  the  radius  of  length  equal  the  radius  rod.  For  a 
reversing  gear  the  link  is  continued  beyond  the  centre  or  pin  from  which 
it  is  hung. 

Another  form  of  gear  was  used  in  Germany  by  Herr  Kaiser,  of  Berlin, 
and  is  very  simple.  Two  lugs  project  from  the  eccentric  strap  at  right 
angles.  To  one  of  them  the  valve  stem  is  attached,  and  the  other  is 

guided  in  a  slot  which  can  be  placed 
at  different  inclinations  with  line  of 
motion.^,  When  the  slot  is  in  the  line 
of  the  motion,  the  valve  is  moved  as 
if  by  a  single  eccentric  found  in  the 
diagram  as  follows: 

Set  off  on  the.line'of  the  motion 
the  real  eccentric  radius,  and  at  right 
angles  to  the  motion,  a  distance 
equal  to  the  real  eccentric  radius 
multiplied  by  the  ratio  of  the  dis- 
tance from  the  centre  of  the  eccentric 
to  the  centre  of  pin  in  the  valve  stem, 
to  the  distance  from  the  centre  of  the 
eccentric  to  centre  of  pin  in  slider. 


44 


STEAM  VSING;  OR,  STEAM  ENGINE  PRACTICE. 


When  the  slide  is  inclined,  the  amount  of  vertical  movement  of  the 
slide  block  caused  thereby  must  be  added  to  the  eccentric  radius  before 
multiplying  length  of  the  lugs  by  the  above  ratio:  as  the  sum  of  these 

two  movements  is 
used  it  is  apparent 
that  this  motion  is 
not  well  suited  for 
a  reversing  gear. 

Instead  of  a 
slide  a  swinging 
link  is  often  used, 
and  by  moving  the 
point  of  suspen- 
sion in  an  arc  with 
a  centre  at  the 
middle  point  of 
the  motion  a  very 
good  distribution 
is  obtained. 


FIG.  24. 


In  all  the  foregoing  motions,  or  valve  gears,  we  have  considered  the 
valve  as  the  ordinary  slide.  By  examining  the  valve  diagrams  already 
given,  we  find  that  when  an  early  cut-off  is  given  by  the  use  of  lap  the  ec- 
centric has  to  be  set  forward,  and  that  either  release  occurs  very  early,  or 
if  this  be  prevented  by  giving  lap  on  the  exhaust 
side  the  exhaust  closes  early  and  cushion  begins. 
Now  just  where  it  is  best  to  stop  in  either  direc- 
tion has  not  been  decided,  but  the  greater  the 
clearance  and  number  of  revolutions  the  earlier 
the  cut-off  can  be  used  with  advantage.  With  8 
per  cent,  clearance  and  less  than  100  revolutions 
it  is  not  desirable  to  cut  off  before  half  stroke, 
but  if  the  speed  be  increased  to  over  300  revolu- 
tions a  cut-off  at  one-fourth  stroke  may  be  em- 
ployed. If  the  travel  of  the  valves  on  a  loco- 
motive for  full  gear  be  4|  to  5  inches,  for  a  lead 
of  i"e  inch  at  full  gear,  and  -,56  inch  at  mid  gear, 
a  steam  lap  of  f  inch  and  no  exhaust  lap  will 

secure  excellent  results;  but  if  the  engine  was  never  to  run  at  a  speed 
of  over  20  miles  an  hour,  an  exhaust  lap  of  |  inch  could  be  used  to 
advantage.  Most  builders  of  stationary  engines  give  so  much  exhaust  lap 
that  a  considerable  back  pressure  is  caused,  and  the  engines  can  not  be 
run  at  high  speed,  and  for  two  reasons:  1st,  that  the  steam  does  not  get 
out  of  the  cylinder  fast  enough,  and,  2nd,  there  is  not  enough  cushion  to 
tase  up  the  fling  of  the  connections  at  high  speed.  An  early  release  and 
strong  cushion  are  required  for  high  speeds. 

At  moderate  speed  an  early  release  and  strong  cushion  deadens  the 
motion  of  the  engine  over  the  centres,  and  the  use  of  two  slide  valves. 


u 
FIG.  25. 


O.V  VALVE 


45 


one  on  top  of  the  other,  was  suggested  by  Meyer.  A  false  valve  seat  was 
suggested  by  Eankine,  with  the  object  of  obtaining  a  quicker  cut-off, 
the  seat  being  moved  by  one  eccentric  while  the  valve  was  moved  by 
another.  In  this  way  the  effect  of  an  eccentric  with  greater  throw  was 
obtained. 

The  first  change  consisted  in  making  the  steam  chest  in  two  cham- 
bers. In  the  one  next  the  cylinder  the  ordinary  slide  was  employed  while 
the  steam  came  in  through  openings  from  the  other  chamber,  these  open- 
ings were  covered  by  a  simple  slide  moved  by  an  eccentric.  Thus  the 
inlet  and  exhaust  were  regulated  by  the  ordinary  slide,  but  the  second  one 
cut  off  the  supply  of  steam.  As  the  principal  objection  to  this  was  the 
large  clearance  space  left  in  the  main  steam  chest  and  the  consequent 
waste  of  steam,  the  Meyer  gear  became  the  favorite. 


isnffifcz^ 


FIG.  26.    THE  MEYER  YALVE. 


The  use  of  an  expansion  valve  on  the  back  of  the  main  valve  allows 
the  main  valve  to  govern  the  admission,  release,  and  cushion,  but  the  cut- 
off is  effected  by  the  expansion  slide  closing  the  steam  ports  of  the  main 
valve.  This  combination  enables  the  cut-off  to  take  place  more  quickly 
with  the  sum  of  the  motions  of  the  two  valves. 

In  Fig.  26,  A  A  are  the  steam  ports  and  B  the  exhaust  port  in  the  cyl- 
inder metal;  C  C  are  the  steam  ports  and  D  the  exhaust  port  in  the  main 
slide.  The  main  slide  is  moved  by  rod  E,  the  plates  G  G,  on  the  top  of 
the  main  slide,  by  rod  F.  Steam  is  usually  admitted  by  the  outer  edges  of 
the  cut-off  plates. 

The  eccentric  of  the  expansion  valve  is  usually  placed  in  line  with  the 
crank,  either  on  the  same  or  opposite  side  of  the  shaft.  This,  however,  is 


46 


STEAM  USING;  OR,  STEAM  ENGINE^PRACTIGE. 


not  essential,  for  there  are  four  ways  in  which  the  cut-off  may  be  varied  by 
means  of  an  expansion  valve: 

1.  By  changing  the  lap  of  the  expansion  valve,  usually  by  means  of  a 
right  and  left  thread  on  the  valve  stem. 

2.  By  changing  the  travel  of  the  expansion  valve,  usually  by  means 
of  a  radius  rod  joined  to  the  valve  stem,  and  a  rocker  link  moved  by  the 
eccentric. 

3.  By  moving  the  eccentric  round  the  shaft,  of  which,  perhaps,  the 
"Buckeye  Engine"  is  the  best  example. 

4.  By  the  use  of  a  link  motion  for  the  expansion  valve. 


FIG.  27. 

We  shall  examine  hereafter  these  methods  more  fully;  but  to  begin 
with  will  take  up  the  case  in  which  the  expansion  valve  is  without  lap, 
and  is  moved  by  an  eccentric  placed  opposite  the  crank,  the  main  valve 
being  without  lap  or  lead,  or,  "line  and  line,"  having,  of  course,  its  eccen- 
tric set  at  right  angles  to  the  crank.  The  valve  diagram  may  be  drawn 
from  the  known  position  of  the  eccentrics,  each  valve  being  represented 
by  its  own  distance  circle. 

In  Fig.  27,  let  C  B  be  the  diameter  of  the  distance  circle  for  the  main 
valve  and  C  A  the  diameter  of  the  distance  circle  of  the  expansion  valve. 


ON  VALVE  GEAR. 


Then,  it  being  remembered  that  with  the  piston  at  the  right  end  of  the 
cylinder,  the  position  of  the  crank  arm  is  C  A,  the  expansion  valve  is 
farthest  from  its  mid  position  and  the  main  valve  is  at  its  mid  position. 
As  the  crank  moves  on  towards  the  position  C  F,  the  main  valve  rapidly 
opens  the  port  while  the  expansion  valve  moves  inward,  at  first  slowly,  but 
with  increasing  speed.  At  C  F  it  is  evident  that  the  main  valve  and  ex- 
pansion valve  are  at  the  same  distance  from  mid  position.  If,  therefore, 
there  be  no  lap  on  the  expansion  slide,  it  will  at  this  point  cover  and 

close  the  opening  in  the 
main  valve,  and  C  F  is 
therefore  the  position  of 
the  crank  at  cut-off.  The 
release  of  steam  to  the 
exhaust,  being  under  the 
main  valve,  can  in  no  way 
be  dependent  upon  the 
\A*  upper,  or  expansion 
valve;  but  there  is  one 
thing  to  be  carefully 
guarded  against,  which 
with  this  arrangement 
might  happen:  the  main 
valve  moves  on  outward 
and  the  expansion  valve 
inward,  until  at  C  B  the 
port  in  the  main  valve  is 
wide  open,  while  the  ex- 
pansion valve  is  at  mid 
position.  The  continuation  of  the  motion  draws  the  main  valve  back,  grad- 
ually closing  the  port  while  the  expansion  valve  is  now  moving  beyond  mid 
position  and  would  of  itself  cover  the  cylinder  port  if  placed  thereon.  At 
C  D,  for  instance,  the  main  valve  has  not  yet  returned  to  the  centre  by  the 
amount  C  E,  -while  the  expansion  valve  is  past  the  centre  by  the  amount  C 
E? '.  We  see  that  in  this  case  there  is  no  risk  of  opening  the  steam  before 
the  end  of  the  stroke  is  reached,  which  was  the  danger  to  be  shunned.  Of 
course,  at  the  end  of  the  stroke  steam  is  admitted  to  the  other  end  of  the 
cylinder  by  the  main  valve,  its  port  at  that  end  having  been  uncovered  by 
the  expansion  valve  when  the  crank  was  in  the  position  (7  D'. 

If  with  the  given  eccentrics  we  should  desire  to  have  the  cut-off  take 
place  before  the  crank  reach  C  F,  we  must  add  lap  to  the  expansion  valve 
so  that  its  edge  shall  meet  and  cover  the  port  in  the  main  valve  before  the 
expansion  valve  becomes  central  thereto.  On  the  other  hand,  if  the  cut- 
off is  to  come  after  C  F.  a  strip  must  be  taken  from  the  edge  of  the  expan- 
sion valve  which  must  meet  the  port  of  the  main  valve  after  the  slide  has 
become  central  thereto,  or  the  lap  must  be  negative.  We  will  consider 
this  case  more  fully  hereafter.  With  the  simple  figure  we  readily  see  the 
effect  of  changing  the  angular  position  of  the  eccentrics  on  the  shaft, 


FIG.  28. 


48 


STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


for  the  main  valve  is  rarely  set  without  lead  cushion  or  a  more  prompt 
release. 

If  the  expansion  eccentric  be  brought  nearer  the  main  eccentric,  or 
moved  backwards  on  the  shaft,  we  see  in  Fig.  28  that  the  intersection  of 
the  two  circles  takes  place  later,  and  that  it  may  range  to  the  end  of  the 
-stroke,  or  more  strictly  speaking,  to  the  cut-off  given  by  the  main  valve 
due  to  its  lap. 


FIG.  29. 


It  may  also  be  seen,  that  in  the  use  of  an  expansion  valve  without  lap 
the  effect  of  a  change  of  travel,  see  Fig.  29,  in  the  expansion  valve,  the 
position  of  its  eccentric  remaining  the  same,  will  also  vary  the  cut-off 
through  a  considerable  range,  but  in  this  case  we  must  expect  inconven- 
ience to  arise  from  the  greater  length  of  steam  chest  required  to  accom- 
modate the  increased  travel. 

The  effect  of  changing  the  lap  on  the  expansion  valve  is  best  examined 
by  combining  the  distance  circles  of  the  two  valves  as  follows,  see  Fig.  30: 

Take  as  before,  C  B  and  C  A,  the  distance  circles  of  the  main  valve  and 
expansion  valve,  respectively.  Join  A  B  and  draw  C  G  parallel  to  A  B, 
and  B  G  parallel  to  A  C.  Upon  C  G  as  a*  diameter  draw  a  circle.  Then, 
for  any  position,  as  C  D,  of  the  crank,  it  may  be  easily  shown  that  the  dis- 
tance of  the  centre  of  the  main  valve  from  the  centre  of  the  expansion 


ON  VALVE  GEAR. 


49 


FIG.  30. 


valve,  CD—  C  E  =  E  D,  is  equal  to  the  chord,  C  L,  of  the  arc  of  this  last 
circle  intercepted  by  the  crank  arm.  Therefore,  the  circle  C  G  may  be 
regarded  as  a  resultant  distance  circle  giving  the  position  of  the  expan- 
sion valve  upon  the  back  of  the  main  valve,  without  regard  to  the  motion 
of  the  latter.  If  there  be  no  lap  on  the  expansion  valve,  we  find  it  central 
with  the  main  valve  at  C  F,  which  is  at  right  angles  to  A  B;  and  we  have 
already  seen  that  with  positive  lap  the  cut-off  takes  place  before  C  F,  while 
with  negative  lap  it  takes  place  after  CFha.s  been  passed.  Thus  we  see 
that  by  cutting  from  the  edge  of  the  expansion  valve,  or  by  increasing  the 
negative  lap,  we  can  delay  the  cut-off  till  C  G  is  reached,  at  which  point 
the  expansion  valve  just  closes  the  port  in  main  valve  for  an  instant  only, 
and  the  steam  continues  to  pass  into  cylinder  until  main  valve  closes.  In 
order  that  the  expansion  valve  may  not  open  again  before  the  main  valve 
closes,  it  must  close  the  port  in  the  main  valve  at  C  B,  or  at  half  stroke  in 
the  case  before  us;  that  is,  the  distance  of  the  edge  of  the  expansion  valve 
from  the  far  edge  of  the  port  in  main  valve,  when  both  are  in  mid  position, 
must  not  exceed  C  B  =  C  A'.  This  distance  evidently  depends  for  its 
value  upon  the  lap  of  the  expansion  valve. 

If  the  cut-off  is  variable,  its  maximum  limit  should  not  be  beyond  the 
point  of  cut-off  of  the  main  valve;  if  it  is  coincident  with  that  of  the 
main  valve,  it  is  evident  that  the  diameter,  C  G,  coincides  with  the  posi- 
tion of  crank  arm  when  the  main  valve  closes,  and  equals  the  distance  of 


50 


AM  USING;  Oil,  STEAM  ENGINE  PRACTICE. 


the  edge  of  expansion  valve  from  far  edge  of  port  as  before  stated.  We 
have  thus  a  limit  which  we  did  not  meet  with  in  our  former  case.  The 
remedy  is  to  increase  the  throw  of  the  expansion  eccentric,  thereby  ren- 
dering the  angle  C  A  B  more  acute,  or  else,  of  course,  to  move  the  expan- 
sion eccentric  nearer  the  main  eccentric. 

By  proper  use  of  the  distance  circles  and  resultant  circle  all  problems 
on  the  Meyer  valve  gear  may  be  readily  solved. 

NOTE.— Figures  31,  32  and  33  work  from  the  left  instead  of  right,  as  heretofore. 


We  will  illustrate  by  a  few  examples: 

Given,  the  lap  and  lead  of  the  main  valve,  and  the  travel  of  both  valves; 
to  find  lap  of  the  expansion  valve  for  a  given  cut-off. 

First,  in  Fig.  31,  from  C  set  off  horizontally  C  D  the  lap  and  D  E  the 
lead  of  the  main  valve,  and  with  C  F  the  half  travel  and  E  F  a  vertical  line, 
construct  the  right  angle  triangle  C  E  F.  On  C  F  as  a  diameter  draw  the 
main  valve  distance  circle,  and  the  lap  arc  D  Kf  defines  the  crank  position 
C  K  when  the  main  valve  closes.  Set  off  C  G  the  half  travel  of  the  expan- 
sion valve  with  the  eccentric  opposite  the  crank,  and  join  G  F.  On  C  H, 
equal  and  parallel  to  G  F,  draw  the  resultant  distance  circle;  and  where  it 
meets  C  I,  the  position  given  for  the  crank  at  cut-off,  gives  CD,  the 
negative  lap  of  the  expansion  valve,  which  we  carry  round  to  J  in  order 
to  see  that  by  the  time  the  expansion  valve  again  uncovers  the  port  of  the 
main  valve  at  C  J,  the  main  valve  has  already  closed  the  cylinder  port 
at  C  K. 


ON  VALVE  GEAR. 


51 


Given,  the  lap,  lead  and  travel  of  the  main  valve,  and  the  travel  of  an 
expansion  valve  having  no  lap;  to  find  position  of  expansion  eccentric  to 
produce  a  given  cut-off. 

Find  in  Fig.  32  the  distance  circle  and  closure  of  the  main  valve,  as 
before,  and  let  C I  be  the  crank  for  given  cut-off.  With  I,  where  this  inter- 
sects the  distance  circle,  as  a  centre,  and  with  C  as  the  centre,  swing  radii 
C  A  and  I  A,  each  equal  to  £  the  travel  of  the  expansion  valve,  denning  by 


FIG.  32. 

their  intersection  at  A,  the  centre  of  the  distance  circle  for  the  expansion 
valve  passing  through  I  and  C.  The  position  of  the  expansion  eccentric 
is  180°— angle  E  CA  ahead  of  the  crank,  or  distant  from  the  main  eccentric 
by  the  angle  F  C  A.  If  the  point  A  falls  above  C  M  drawn  at  right  angles 
to  C  K,  the  slide  will  not  open  the  port  until  after  the  main  valve  has 
closed.  But  if  A  falls  to  the  left  of  C  M,  a  new  eccentric  must  be  taken. 

Given,  the  same  data,  viz.:  lap,  lead  and  travel  of  main  valve,  and  lap 
and  travel  of  expansion  valve;  to  find  position  for  expansion  eccentric  to 
produce  a  given  cut-off. 

In  Fig.  33,  draw  C  F  and  C  Kas  before,  and  on  C  /,  the  given  position 
of  crank  at  cut-off,  set  off  C  A,  the  negative  lap  of  the  expansion  valve. 
From  A  draw  A  J  at  right  angles  to  C  A,  and,  with  the  half  travel  of  the 
expansion  valve,  define  from  E  on  A  Jthe  point  L.  C  M,  equal  and  par- 
allel to  L  F,  is  the  position  sought  for  the  expansion  eccentric  arm. 


52 


STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


Other  problems  will  readily  be  solved  if  there  be  sufficient  data,  but 
we  think  we  have  given  the  most  important,  and  enough  to  show  the  flex- 
ibility and  power  of  the  method. 

When  such  valves  as  described  are  used,  the  engine  is  said  to  have  an 
expansion  valve.  When  the  cut-off  can  be  changed  while  running  or  when 
still,  the  engine  is  said  to  have  variable  expansion.  When  the  cut-off  is 
changed  by  the  action  of  the  engine  itself,  owing  to  change  of  speed,  it  is 
called  automatic  expansion. 


FIG.  33. 


When  the  cylinder  is  so  long  that  a  single  slide  becomes  inconvenient, 
two  exhaust  ports  are  used,  and  the  valve  is  divided  into  two  portions,  one 
for  each  end  of  the  cylinder.  Care  must  here  be  taken  that  the  exhaust 
port  is  not  open  to  the  steam  by  the  valve  having  too  much  travel. 

Sometimes  a  piston  valve  is  used,  which  consists  of  two  pistons  on  the 
valve  stem,  either  arranged  to  give  steam  space  between  the  pistons  and 
the  exhaust  connections  at  the  end  spaces,  or  through  the  hollow  piston; 
or  with  the  exhaust  port  between  the  pistons  and  the  steam  space  at  the 
ends.  Examples  of  these  arrangements  are  given  on  page  55.  The 
graphical  method  heretofore  used  will  answer  for  all  these  varieties. 

In  large  engines  and  in  many  paddle-wheel  steamers  four  valves  are 
used,  generally  "Equilibrium  poppets,"  or  the  older  "Cornish  equilibrium:" 
these  were  introduced  at  a  very  early  period  in  the  history  of  the  steam 
engine.  The  single  unbalanced  poppet  is  still  used  in  small  engines  on 
the  Mississippi,  and  a  very  common  arrangement  is  a  "relief  valve,"  or  a 
small  poppet  on  the  top  of  a  large  one,  the  small  one  being  lifted  first  and 
its  continued  movement  raising  the  large  one.  By  the  use  of  moveable 
seats  and  poppets  set  on  the  valve  stem  the  "balance"  may  be  carried  to 


OV  VM.VK 


53 


any  desired  extent.  The  ordi- 
nary forms,  as  also  the  Cornish, 
require  one  end  of  the  valve  to 
pass  through  the  seat  for  the 
other  end,  thus  limiting  the 
degree  of  closeness  of  the 
agreement  of  areas  or  the  "bal- 
ancing." 

The  stems  of  these  poppets 
are  usually  moved  by  levers, 
worked  by  cams  on  one  or  more 
auxilliary  rock  shafts  placed 
near  the  cylinder.  The  valves 
are  always  moved  vertically. 
The  movement  of  the  rock 
shafts  is  usually  effected  by  an 
eccentric  on  the  main  shaft. 
On  the  Mississippi  river,  in- 
stead of  an  eccentric,  a  cam  is 
used.  One  cam  is  used  for  full 
stroke  in  either  direction,  and 
the  reversing  is  done  by  hook- 
ing to  either  one  of  a  pair  of 
arms  on  a  rock  shaft;  a  second 
cam  is  used  for  cutting  off  for 
the  steam  valves  when  running 
ahead  only,  the  exhaust  being 
moved  by  the  full  stroke  cam. 
The  forms  of  the  cams  are  such 
as  to  give  very  rapid  move- 
ments of  opening  and  closing, 
as  will  be  seen  from  the  indi- 
cator diagrams  taken  from  the 
steamer  Phil.  Chappel,  shown 
in  Chapter  IV.  The  shape  of 
cams  and  arrangement  of  valve 
gear  is  shown  in  the  drawings 
of  the  engines  of  the  steamer 
"Montana,"  as  applied  to  the 
Mississippi  boats,  and  also  their 
application  to  Engine  No.  1, 
High  Service,  St.  Louis  Water- 
works, which  is  an  example  of 
the  application  usual  near  New 
York,  and  on  the  North  Eiver 
class  of  boats. 

When    poppet  jvalves  [are 


54 


STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


used  with  a  drop  cut-off,  there  is  a  shock  which  causes  rapid  wear  on  the 
valve  and  seat  unless  a  dash  pot  is  used  to  prevent  it.  At  a  speed  of  more 
than  30  revolutions  per  minute,  poppet  valves  do  not  appear  to  give 
entire  satisfaction,  but  with  a  small  number  of  revolutions  they  work  well. 
We  have  seen  them  used  up  to  70  revolutions,  but  have  generally  found 
upon  enquiry  that  very  frequent  grinding  was  required. 


FIG.  35.    DOUBLE  VALVE. 

From  the  variations  in  steam  pressure  and  w^ork  on  stationary  engines 
there  necessarily  resulted  variations  in  speed,  which  for  many  reasons  is 
exceedingly  undesirable,  and  we  find  that  Watt  very  soon  produced  his 
centrifugal  governor,  applied  to  the  throttle  valve  in  the  well  known  man- 
ner. Under  various  forms  this  arrangement  is  still  the  most  common  one, 
and  for  small  variations  of  speed  it  is  perhaps  as  good  as  anything  yet 
devised. 

For  large  variations  in  speed  it  was  found  that  with  light  loads  the 
engine  was  so  throttled  that  the  initial  pressure  in  the  cylinder  was  much 
below  the  boiler  pressure,   and  a  manifest  waste  of  steam  resulted,  the 
steam  not  yielding  the  amount  of  work  which  might  be  obtained  there- 
from, and  a  class  of  engines 
with  four  valves  and  a  "drop 
cut-off,"    regulated  by  the 
governor,  was  introduced  by 
Mr.  Geo.  H.  Corliss. 

The  engine  introduced 
by  Mr.  Corliss  was  in  many 
respects  a  very  great  im- 
provement. The  valves  were 
placed  close  to  the  cylinder 
and  were  rotary  instead  of 
sliding.  The  clearance  space 
was  very  much  reduced  and 

the  engines  became  very  successful.  The  drop  cut-off  regulated  by  the 
governor  kept  the  initial  pressure  of  steam  in  the  cylinder  well  up  to  the 
boiler  pressure,  and  changes  of  speed  were  followed  so  closely  by  changes 
of  cut-off,  that  in  engines  well  proportioned  to  the  work  an  economy 
never  before  attained  was  reached. 

In  the  United  States  the  term  Corliss  is  applied  only  to  engines  with 
the  rotative  Corliss  valve,  but  in  Europe  it  has  been  used  for  any  engine 
with  cut-off  regulated  by  the  governor,  as  this  was  first  successfully 


FIG.  36.    TKICK'S  VALVE. 


OX  YAI.VK  <;EAH. 


55 


VALVE  SEAT. 


FIG.  37. 


Exhaust 

PISTON  VALVES. 


SECTION  THROUGH 
VALVE  SEAT. 


applied  by  Mr.  Corliss.  A  host  of  imitators  soon  followed,  each  with  a 
variation  in  the  "let-off"  gear,  and  with  slide  and  poppet  valves  moved 
by  one  or  two  eccentrics.  Since  the  expiration  of  the  Corliss  patents  a 
crop  of  designs  has  come  forward,  all  distinguished  by  the  appendix 
"Corliss."  Of  these  we  shall  illustrate  one  built  by  Messrs.  E.  P.  Allis  & 
Co.,  of  Milwaukee,  Wis.,  from  the  designs  of  their  manager,  Mr.'  Edwin  F. 
Reynolds,  and  placed  in  the  St.  Louis  Cotton  Mill. 


FIG.  38.    DOUBLE  POPPET  VALVE. 


56  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


A  modification  of  the  Corliss  engine  is  manufactured  by  Mr.  Jerome 
Wheelock,  of  Worcester,  Mass.,  in  which,  with  only  two  ports  and  two 
main  valves,  the  steam  admission  is  closed  by  two  other  valves  adjacent  to 
the  main  valves  and  worked  from  them  by  clutch  links;  all  four  valves  are 
of  the  Corliss  type.  As  built,  the  only  objection  to  these  engines  is  the 
difficulty  of  arranging  the  cushion  to  the  varied  requirements  of  practice. 

The  production  of  an  engine  with  cut  off  regulated  by  the  governor, 
but  without  the  let-off,  or  drop  gear,  which,  by  the  way,  is  not  adapted  to 
higher  speeds  than  120  revolutions,  has  been  secured  in  the  Buckeye  and 
the  Porter- Allen  engines.  In  the  former,  two  ports,  a  balanced  slide  valve 
and  an  expansion  slide  are  used,  the  cut-off  being  changed  by  the  gover- 
nor, and  that  by  turning  the  expansion  eccentric  round  the  shaft  by  the 
centrifugal  force  of  two  weights  held  back  by  springs  in  a  manner  easily 
understood  from  the  drawings.  In  the  Porter-Allen  engine  there  are  four 
ports  and  the  steam  valves  are  balanced  slides  moved  by  an  expansion 
link,  already  explained,  and  the  exhaust  is  moved  from  the  end  of  the 
same  link.  We  shall  give  illustrations  of  these  in  Chapter  IV  which  will 
more  fully  explain  their  principles. 

In  large  engines  using  slide  valves  the  ports  are  often  made  double, 
the  valves  having  passages  cast  in  them  connecting  the  steam  and  exhaust 
ports.  This  in  no  way  affects  the  valve  diagram  constructions  already 
given. 

When  the  cylinders  are  over  12  inches  in  diameter  it  is  well  to  connect 
the  metal  across  the  ports  by  bridges,  so  that  the  heads  shall  not  be  ren- 
dered weak,  or  the  pull  on  the  bolts  concentrated  on  those  next  the  ends 
of  the  ports. 

In  some  excellent  examples  of  engines  with  four  ports,  gridiron  slides 
are  used,  working  transversely  to  the  cylinders.  These  slides  are  moved 
usually  by  cams  on  a  "lay  shaft,"  and  the  cut-off  is  changed  by  shifting 
the  cams  along  the  shaft,  bringing  different  portions  of  the  cam  face  with 
different  angular  forces  into  action.  A  good  example  of  this  is  found  in 
the  "Howard"  engine.  By  this  means  a  very  sharp  opening  and  closing- 
can  be  given  the  valves,  but  in  small  engines  a  larger  clearance  is  required 
than  is  desirable.  Each  valve  can  be  adjusted  by  itself,  which  is  a  de- 
sirable feature. 

Valve  gear  of  this  class  has  been  employed  with  great  success  by  Mr. 
E.  D.  Leavitt,  Jr.,  in  his  celebrated  pumping  engines. 


CHAPTER      III. 
THE  QUANTITY  OF  STEAM  WHICH  MIGHT  BE  AND  WHICH  IS  USED. 

Although  we  have  no  such  engines  as  that  which  was  described  in  the 
preceding  chapter,  it  is  desirable  to  assume,  for  the  purposes  of  computa- 
tion, and  in  order  to  obtain  a  view  of  complex  operations  in  detail,  that  we 
use  the  steam  in  a  non-conducting  vessel  whose  volume  can  be  varied:  in 
other  words,  in  a  cylinder  constructed  of  material  which  cannot  conduct 
heat.  But  we  must  be  very  careful  to  remember  that  no  such  engine  at 
present  exists,  and  that  we  shall  have  to  adapt  the  deductions  made  from 
such  a  case  to  real  engines.  Serious  disappointment  and  useless  expense 
have  resulted  from  ignoring  this  fact  in  designing  engines,  and  much  dis- 
cussion on  the  subject  has  arisen. 

In  the  case  of  engines  using  steam  non- expansively,  or  without  "cut- 
ting-off,"  we  should  have  very  little  trouble  in  computing  the  work  done 
by  a  pound  weight  of  steam,  or  the  number  of  pounds  of  steam  used  to 
obtain  a  horse-power  of  work  in  the  cylinder,  as  we  shall  very  easily  see. 

We  know  that  the,  equivalent  of  a  unit  of  heat  is  772  foot-pounds  of 
work,  and  that  33,000  foot-pounds  of  work  per  minute  is  the  standard 
horse-power: 

33,000  75 

Hence,   ^-     =  42100  = 

the  number  of  heat  units  per  minute  which  have  to  be  expended  to 
obtain  a  horse-power,  provided,  we  had  any  means  of  transforming  heat 
into  work  without  waste.  And 

75 
42100  x  6ft  =  2,565  heat   units,   the  equivalent  of  a  horse-power  per 

hour. 

In  a  full  stroke  engine  with  non-conducting  cylinder,  and  without 
other  losses,  AVC  should  only  have  to  divide  2,565  by  the  number  of  heat- 
units  given  in  the  Table  of  the  "Properties  of  Saturated  Steam, "  Chapter 
I,  as  heat  expended  in  doing  external  work,  or  external  heat,  for  one 
pound  weight  of  steam  at  the  boiler  pressure,  to  obtain  the  number  of 
pounds  of  water  which  must  be  boiled  per  hour  to  furnish,  or  to  exert,  one 
horse- power  per  hour  for  the  work  of  the  steam  in  the  cylinder. 

There  are  many  reasons  why  the  amount  of  steam  used  per  hour,  and 
per  horse-power,  should  vary  from  this: 

1.  The  steam  passages  may  be  too  small  to  maintain  the  steam  supply 
at  the  boiler  pressure. 

2.  The  boiler  may  be  so  small  in  steam  room  that  the  pressure  in 
both  boiler  and  cylinder  may  fall  during  the  stroke. 


58  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

3.  The  clearance,  or  waste  space,  in  the  cylinder  will  be  filled  with 
steam  at  boiler  pressure  before  the  piston  starts,  which  will  be  discharged 
at  exhaust  without  having  performed  any  work. 

4.  The  fact  that  the  cylinder  and  piston  receive  heat  when  the  steam 
comes  in  and  give  it  out  while  the  steam  goes  out.    More  will  be  said  on 
this  point  later. 

The  power  exerted  by  the  steam  in  the  cylinder  is  subjected  to  the 
following  further  losses  before  it  can  be  utilized: 

1.  The  vapor,  or  steam,  on  the  exhaust  side  of  the  piston  has  to  be 
pushed  out  of  the  cylinder  by  the  advancing  piston  against  the  back 
pressure. 

2.  Mechanical  work  is  absorbed(  in  friction  by  the  piston  slides  and 
connections  of  non-rotative  engines,  and  by  the  main  bearings  of  rotative 
engines. 

These  several  points  give  rise  to  the  measurement  of  horse-power  in 
three  ways: 

1.  The  number  of  horse-power  really  exerted  by  the  steam — called 
in  English  the  total,  and  in  French  the  absolute,  horse-power. 

2.  The  number  of  horse-power  exerted  by  the  steam  after  deducting 
that  expended  in  sweeping  out  the  exhaust.     This  is  given  by  the  ordinary 
indicator  measurement,  and  is  called  the  Indicated  Horse  Power:  it  is 
what  is  usually  understood  by  the  phrase  Horse-power,  without  qualifica- 
tion, in  the  United  States. 

3.  The  power  which  may  be  taken  from  the  shaft  by  a  dynamometer, 
or  by  a  belt,  which  represents  the  power  of  the  engine  to  do  useful  work 
outside  of  itself.     This  is  called  the  Net,  or  Effective  Horse  Power. 

As  these  three  quantities  are  for  any  given  measurement  produced  by 
the  same  amount  of  water  boiled,  we  find  that,  dividing  the  quantity  of 
water  used  per  hour  by  the  number  of  horse-power,  we  have  also  three 
quotients,  viz.:  The  number  of  pounds  used  per  hour  for  Total,  for  Indi- 
cated, and  for  Net  Horse  Power.  These  may  be  considered  as  the  "stu- 
dent's," the  "ordinary,"  and  the  "commercial"  standards  of  measurement. 
Engineers  are  obliged  to  retain  all  three  of  these  quantities,  for:  In  any 
given  engine  with  given  speed  and  circumstances,  the  work  expended  on 
the  exhaust  and  friction  is  nearly  constant,  and  hence,  the  greater  the 
power  of  the  steam  used  the  less  is  the  percentage  of  that  uselessly 
expended. 

In  illustration  of  the  process,  referred  to,  we  give  the  following 
examples: 

Example  I.  What  is  the  minimum  steam  consumption  per  hour  for 
an  engine  using  steam  at  full  stroke,  at  25  Ibs.  pressure  above  the  atmos- 
phere, with  a  vacuum  of  12  pounds,  and  indicating  200  horse-power  for  a 
non-conducting  cylinder?  Clearance  8  per  cent. 

Steam  pressure  =  25  +  15  =  40  Ibs.  above  zero. 
Back  pressure  =  15  —  12  =  3  Ibs  above  zero. 
Pressure  expended  in  obtaining  the  indicated  horse- power  is: 
40  -  3  =  25  +  12  =  37  Ibs. 


QUANTITY  OF  STKAU  f'SKfl.  ETC.  59 

From  the  Table  of  "Properties  of  Steam"  we  find  that  the  external  work 
of  1  pound  weight  of  steam  at  25  Ibs.  pressure  is  equal  to  77  heat  units, 
and  we  should  have  to  use  to  obtain  a  Total  Horse-power,  2,565,  the 
equivalent  of  heat  units  for  a  horse-power  per  hour,  divided  by  77  as 
above,  which  would  give  the  number  of  pounds  of  water  per  hour,  — 
neglecting  clearance. 

To  obtain  the  indicated  horse  -power:  we  have  ~7y    x  ^  =  pounds 

per  hour. 

If  the  friction  of  the  engine  absorbs  as  usual  2  Ibs.  pressure,  we  shall 

have     77     x   35  =  Ibs.  of  water  per  net  horse  -power  per  hour. 

40 
The  number  of  Total  Horse-power  is  200  x  3_  . 

37 
The  number  of  Net  Horse  -power  is  200  x  ^  . 

The  water  used  per  hour  neglecting  clearance  is: 

2565        40 
77      <   37  X  200' 

and  including  clearance 

2|75  x   3°  x  200  x  1.08. 

Working  out  these  figures,  we  shall  have: 
Water  per  Total  Horse-power  per  hour  =  33.3. 
Water  per  Indicated  Horse-power  per  hour  =  36.0. 
Water  per  Net  Horse-power  per  hour  =  38.0. 
Water  per  hour  =  200  x  1.08  x  36  =  7,720  pounds. 
When  the  cylinder  is  not  non-conducting  a  much  larger  quantity  of 
water  will  be  consumed. 

Example  II.    The  following  figures  illustrate  about  as  bad  a  case  in 
actual  practice,  as  ever  came  within  the  author's  experience: 
Steam  pressure  60  Ibs.  above  atmosphere. 
Back  45    tt 

Steam  pressure  75  Ibs.  above  zero. 
Back  60    " 

Acting  pressure  on  piston  75  —  60  =  15  Ibs. 
External  heat  for  60  Ibs.  =  79  heat  units. 


Water  per  Total  Horse-power  -        =  32.4  Ibs. 

2565        75 
Water  per  Indicated  Horse-power    79     x   -     =  162  Ibs. 


60  STEAM  USING;  OH,  STEAM  ENGINE  PRACTICE. 

Example  III.  — 

Steam  pressure  205  Ibs.  above  atmosphere. 

Back  2    " 

Steam        "         220    "     above  zero. 

Back  17    " 

Acting       "         183    "     on  piston. 

External  work  for  205  Ibs.  =  85  heat  units. 

Water  per  hour  for  Total  Horse-power    g5     =  30.2. 

"     for  Indicated      "  -gg-  x   2Q3  =  32.3. 


We  see  from  examples  I  and  III  that,  although  in  the  intrinsic  work 
of  the  steam  there  is  not  much  gained  by  the  use  of  high  pressure  steam 
in  full  stroke  engines, 

33.3  —  30.2         3 
~30~    =9^  per  cent., 

yet  that  high  pressure  non-  condensing  engines  may  be  practically  more 
economical  than  low  pressure  condensing  ones;  for  supposing,  as  we  did, 
that  3  pounds  moved  the  engine  only,  we  have: 

38.0  —  33.2  6 

38.0          =  12f<)  Per  cent" 

as  the  practical  gain  in  the  cost  of  a  Net  horse-power:  and  there  are  the 
further  advantages  that  the  loss  by  the  use  of  a  conducting  cylinder  is 
less,  and  the  machinery  is  far  less  bulky  and  complex. 

This  is  a  very  fair  comparison  of  the  early  steamboat  engines  when 
working  full  stroke,  as  used  on  the  Atlantic  ocean  and  the  Mississippi 
river.  The  use  of  steam  at  a  very  high  pressure,  not  only  requiring 
cheaper  machinery  and  of  less  weight,  but  actually  using  less  steam  to  do 
the  work,  when  worked  at  or  near  full  stroke. 

The  process  of  computing  the  amount  of  steam  used  by  expanding 
engines  with  non-conducting  cylinders  is  much  less  easy  to  explain,  al- 
though the  work  of  computation  is  but  little  more  difficult. 

In  order  to  study  the  action  of  expanding  gases  it  is  convenient  to 
represent  the  volume  and  pressure  for  any  given  state  and  quantity  by 
distances  set  off  at  right  angles  to  each  other,  on  convenient  scales.  Thus, 
by  the  distance  of  a  point  above  a  line  we  measure  the  pressure,  and  by 
the  distance  of  a  point  to  the  right  of  a  line,  we  measure  the  volume.  For 
a  different  state  of  volume  and  pressure  we  have  a  different  point;  for 
states  of  volume  and  pressure,  differing  little,  we  have  points  near  to- 
gether, and  for  changing  states  of  volume  and  pressure  we  have  a  moving 
point,  which  may  be  considered  to  trace  a  line.  When  a  series  of  changes 
brings  the  gas  back  to  its  original  state,  the  line  traced  will  return  into 
itself. 

The  product  of  a  force  into  a  distance  through  which  it  moves  is 
known  as  energy  exerted,  and  it  is  equal  to  the  product  of  the  resistance 


QUANTITY  OF  STKAM  USED,  ETC.  61 


by  the  distance  through  which  it  is  moved;  or,  what  is  known  as  the  work 
done;  and,  as  in  an  engine  cylinder,  the  moving  force  on  the  piston  is  the 
pressure  times  the  area  of  the  piston,  and,  as  for  a  small  movement  the 
pressure  remains  nearly  the  same,  the  energy  expended  is  the  product  of 
the  mean  pressure,  by  the  piston  area,  by  the  distance  moved;  or  the 
pressure  times  the  change  in  volume  as  the  product  of  the  piston  area  by 
the  distance  moved  by  the  piston  is  the  change  in  volume  occupied.  The 
number  of  cylinders  in  which  such  changes  of  volume  take  place  is 
immaterial,  as  the  total  energy  expended  must  be  the  sum  of  the  ener- 
gies expended  in  all  such  cylinders;  hence,  the  statement,  that  the 
energy  expended  is  the  product  of  the  mean  pressure  by  the  change  in 
volume.  Hence,  also,  the  diagram,  just  explained,  furnishes  the  data 
for  finding  the  energy  expended,  as  the  latter  must  be  represented  by 
the  area  between  the  horizontal  line  of  "no  pressure,"  the  two  verti- 
cals at  the  end  of  the  change  of  volume,  and  the  line  traced  by  the  moving 
point. 

In  any  series  of  changes  in  which  the  original  state  of  volume  and 
pressure  is  again  reached,  the  energy  effectively  exerted  is,  of  course,  the 
difference  between  that  expended  on  the  piston  and  that  exerted  by  the 
piston;  or,  that  which  is  represented  by  the  enclosed  figure. 

The  first  thing  to  be  determined  is  the  curve  of  expansion,  or  the 
curve  which  would  be  drawn  by  an  indicator  attached  to  such  an  expand- 
ing engine  with  a  non-conducting  cylinder;  but  as  no  such  cylinders  ex- 
ist, we  have  to  approximate  the  curve  from  the  table  of  the  "Properties  of 
Steam." 

If  we  set  out  with  the  volume  of  one  pound  weight  of  steam  at  a  given 
pressure,  and  then  assume  it  to  expand  by  any  defined  law  until  its  pres- 
sure has  been  lowered  to  a  given  amount,  we  can  compute  the  external 
work  done  in  changing  the  volume;  then  taking  this  heat  from  the  total 
internal  heat  contained  in  the  steam,  if  we  find  that  the  change  in  inter- 
nal heat  is  less  than  that  required  to  do  the  external  work,  as  by  assump- 
tion we  find  it  in  a  non-conducting  cylinder,  some  of  the  heat  must  be 
supplied  by  the  condensation  of  the  steam  itself,  and  that,  therefore,  the 
volume  must  be  reduced,  and  with  it  the  external  work,  and,  of  course, 
also  the  heat  required  to  do  this  external  work.  By  a  little  care  in  ap- 
proximating, we  shall  arrive  at  such  a  condensation  that  the  change  in  in- 
ternal heat  added  to  the  heat  given  by  condensation  will  just  balance  the 
heat  absorbed  by  the  external  work  of  expansion.  Thus,  a  point  on  the 
expansion  curve  for  the  indicator  diagram  of  steam  expanding  in  a  non- 
conducting cylinder  is  obtained. 

The  assumed  law  of  expansion  may  be  anything,  but  perhaps  the  best 
for  the  purpose  is  that  given  by  the  volumes  and  pressures  of  saturated 
steam,  or,  what  is  known  as  the  "steam  line."  A  common  assumption  is 
that,  the  product  of  the  pressures  and  volumes  is  constant,  though  there 
is  no  basis  for  such  an  assumption. 

The  computation  of  the  work  done  by  the  expansion  can  be  perform- 
ed in  various  ways,  but  for  our  purposes  we  shall  plot  the  steam  line  and 


62 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


compare  the  area  of  the  diagrams  by  any  of  the  methods  or  instruments 
used  for  measuring  indicator  cards. 


8  10 

NUMBER  OF  EXPANSIONS. 
FIG.  39. 


Such  a  steam  line  or  expansion  curve  for  dry  steam  having  been  drawn, 
see  Fig.  39,  and  the  areas  measured:  first,  of  the  rectangle  o  a  b  1  and  next, 
for  the  area  under  the  curve,  we  find  the  quotient  of  the  area  under  the 
curve  divided  by  the  rectangle  area  for  different  expansions  to  be  as  fol- 
lows: 


Area  under 

Area  under 
curve. 

curve. 

Rectangle. 

1  .  .     . 

o 

2 

be    2 

0  68 

3  

b  d    3 

1  12 

4 

6  e    4 

1  33 

5... 

6/5 

1  53- 

8  

I)  n    8 

1.97 

0 

b  h  10 

2.14 

0  .... 

&  i  20 

2.73 

Now,  assuming  85  pounds  as  an  average  steam  pressure,  or,  15  +  85  = 
100  pounds  above  zero,  we  have  for  the  external  work  of  evaporation,  81 
units,  and  for  the  total  internal  work  1,100  units.  Now,  taking  the  rect- 
angle o  a  b  1  in  the  figure  as  representing  the  work  of  81  units,  it  is  clear 
that  the  work  of  expansion,  in  units  of  heat,  will  be  obtained  by  multiply- 


QUANTITY  OF  STEAM  USED,  ETC. 


63 


ing  the  81  units  by  the  number  given  in  the  quotients  above,  which  will 
give  values  as  follows: 


Heat  units   in 
work  of  ex- 
pansion. 


0 
55 
91 

108 
124 
160 
173 
221 


The  terminal  pressures  are  found  by  division  and  subtraction : 
85  +  15  _  15 

r 

The  corresponding  internal  heats  for  dry  steam  are  given  in  the  fol- 
lowing table: 


;• 

Terminal 
pressure. 

Internal 
heat. 

Heat  units  in 
work  of 
expansion  . 

Heat   units  left  af- 
ter deducting  work 
of  expansion  from 
1,100  units. 

1  

85 

1,100 

0 

1,100 

2 

33 

1,090 

55 

1  045 

3  

16 

1,083 

91 

1,009 

4 

8 

1  079 

108 

992 

5  

3 

1,  079 

124 

976 

8  

I 

1,071 

160 

940 

10  

6 

1,069 

173 

927 

20  

11 

1,060 

221 

879 

Now  the  internal  heat  at  the  end  of  expansion  is  less  than  that  given 
for  dry  steam  at  the  same  pressure;  therefore,  a  part  of  the  heat  for  expan- 
sion must  have  been  furnished  by  the  condensation  of  a  portion  of  the 
steam.  But  such  condensation  reduces  the  work  of  expansion  itself  and 
hence  the  condensation  supplies  heat  again  and  so  on.  The  correct  values 
for  the  curve  in  a  non-conducting  cylinder  are  approximated  as  follows: 


r 

Heat  in  dry 
steam. 

Heat  at  end  of 
expansion. 

Excess  re- 
quired from 
condensation. 

Change  in 
Units. 

Change  in 
Excess. 

1  

1,100 

1,100 

0 

o 

2  

3 

1,089 
1  084 

1,045 
1  009 

44 
75 

2 

42 

70 

4 

1  080 

992 

88 

g 

79 

5  

1,079 

976 

103 

12 

91 

,M 

1  071 

MO 

131 

20 

111 

10  

1,069 

927 

142 

23 

119 

20 

1  060 

879 

181 

38 

143 

64 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


But  these  values  are  now  in  error,  for  the  one  is  assumed  on  the  basis 
of  more  external  work  than  has  been  done,  and  the  other  on  less.  The 
true  value  lies  between  them,  and  the  assumption  that  the  true  value 
divides  the  difference  in  the  proportion  of  the  values  found  gives  us  a 
close  approximation. 


T 

Per  cent, 
of 
change. 

Change  in 
units. 

Excess  required  from 
condensation. 

Work  of 
expansion  . 

In  units. 

Per  cent. 

Gain. 

I 

2  ,  

95 
91 
90 

88 
85 
84 
79 

2 
6 
8 
11 
17 
19 
30 

44 

78 
87 
102 
127 
139 
182 

4 

J 

o 

9 
12 
12 
17 

0.67 
1.11 
1.31 
1.50 
1.90 
2.05 
2.55 

3      

4 

5         

8 

10                                 ..... 

20  

From  the  curve  already  drawn  for  Dry  steam,  we  draw  the  new  curve 
by  changing  the  points  for  volume,  reducing  it  by  deducting  the  per- 
centage for  condensation.  The  points  so  found  are  marked  on  Fig.  39, 
with  the  same  letter  accentuated.  A  comparison  of  the  areas  under 
the  new  curve,  between  the  same  volumes,  will  give  the  last  column  of 
figures. 

A  similar  curve  drawn  for  steam  at  25  pounds  pressure,  does  not  differ 
in  the  second  place  of  decimals,  and  for  steam  at  185  pounds  it  only  differs 
by  1  in  the  second  decimals  for  ten  expansions.  The  approximation  made 
is  within  one  heat  unit  and  we  may  therefore  use  these  results  hereafter 
with  confidence,  remembering  that  we  must  obtain  the  last  column  for 
corresponding  values  of  r  for  volumes  not  pressures. 

The  curve  of  expansion  of  steam  in  a  non  conducting  cylinder  has 
been  called  by  Prof.  Kankine,  an  "Adiabatic"  curve,  and  by  Prof.  Clausius 
an  "Isentropic"  curve,  and  these  terms  may  be  met  with  in  all  works  on 
steam,  frequently  adding  to  the  difficulties  of  the  student.  They  will, 
therefore,  not  be  used,  nor  referred  to,  again  in  this  work. 

The  amount  of  steam  required  to  do  the  work  in  a  non-conducting 
cylinder  is  found  by  dividing  the  amount  per  total  horse  power  per  hour 
for  a  non-expanding  cylinder  by  1,  plus  the  ratio  given  in  the  last  column 
of  the  preceding  table,  or,  the  ratio  of  the  total  work  done  compared  with 
that  done  at  boiler  pressure. 

From  a  large  diagram  constructed  by  the  process  described  we  have 
tabulated  the  following  values: 


'jl'.\  XT1TY  OF  STEAM  USED,  ETC. 


65 


PROPERTIES  OF  THE  CURVE  OF  EXPANSION  IN  A  NON-CONDUCTING 

CYLINDER. 


No.  of  Expansions. 

Ratio  of  Total  Area  to 
Area  of  Rectangle. 

Ratio  of   Mean  Total  Ratio    of   Total   Ter- 
to  Initial  Total  Pres-       minal   to   Initial 
sure.                                  Pressure. 

1 

.1                               1.090 

0.991 

0.90 

.2                                   1.180 

.983 

.82 

.3                                   1.261 

.970 

.75 

M                                   1.333 

.952 

.69 

.5 

1.396 

.931 

.64 

.6 

1.459 

.912 

.59 

.8 

1.576 

.866 

.52 

.0 

1.666 

.833 

.46 

.5 

1.873 

.749 

.36   , 

.0 

2.035 

.678 

.30 

.0 

2.278 

.568 

.21 

.0 

2.476 

.493 

.17 

.0 

2.629 

.436 

.14 

7.0 

2.746 

.393 

.12 

8.0 

2.854 

.357 

.10 

9.0                                     2.953 

.328. 

.087 

10.0                                     3.034 

.303 

.077 

11.0                                     3.106 

.282 

.070 

12.0                                     3.169 

.264 

.063 

13.0                                     3.232 

.248 

058 

U.O                                     3.286 

.235 

.053 

16.0                                     3.385 

.211 

.046 

20.0                                     3.547 

,177 

.036 

25.0                                     3.709 

.148 

.028 

30.0                                     3.835 

.128 

.023 

From  the  preceding  table,  and  the  table  of  external  work  of  steam, 
the  following  table  is  computed.  The  first  line,  or  steam  used  for  one 
expansion,  or  full  stroke,  is  obtained,  as  already  explained,  by  dividing 
2,565,  the  number  of  units  of  heat  for  a  horse-power  per  hour,  by  the 
number  of  units  of  heat  for  external  work;  and  the  other  quantities  by 
dividing  these  numbers  by  the  gain  by  expansion,  or  ratio  of  total  area  of 
figure  to  area  of  rectangle.  This  has  also  been  explained.  From  the  ratio 
of  total  mean  pressure  to  initial  pressure,  the  three  next  tables  are  com- 
puted, by  assuming  that  a  back  pressure  of  4  pounds  per  square  inch 
exists  in  the  condensing,  and  16  pounds,  or  1.3  pounds  above  the  atmos- 
phere, in  the  non-condensing  engine.  In  each  case  the  mean  total  pres- 
sure is  found  and  the  back  pressure  deducted.  The  quantity  of  water  per 
total  horse-power  is  then  multiplied  by  the  ratio  of  the  mean  total  to  the 
mean  indicated  pressure,  or  the  pressure  left  to  act  on  the  piston  after 
deducting  the  back  pressure,  4  or  16  pounds  respectively,  to  obtain  the 
consumption  of  water  per  indicated  horse-power  per  hour  in  a  non- 
conducting cylinder. 


66 


STEAM  LTSING:  OR,  STEAM  K \G1XK  PRACTICE. 


COST  PER  HOUR  PER  TOTAL  HORSE-POWER,  IN  POUNDS,  IN  DRY  STEAM  IF 
WORKED  IN  NON-CONDUCTING  CYLINDERS. 


BOILER  PRESSURE  IN  POUNDS  PER  SQUARE  INCH. 

No.  of 

Expan- 

sions.  Atmos. 

0 

20 

40              60 

80 

100     :       120            140     j       180            220 

1 

35.7 

33.7 

32.9          32.5 

32.1 

31.7          31.3 

30.9          110.5          30.2 

1.1         32.7 

31.0 

30.9         29.8 

29.4 

29.0          28.7 

28.3     ,     28.0         27.7 

1.2 

30.2 

28.6 

27.9          27.5 

27.2 

26.8 

26.5 

26.2 

25.9 

25.5 

.3 

27.  G 

26.2          25.5          25.2 

24.8 

24.5 

24.2 

23.9 

23.7 

23.4 

.4 

26.1 

24.7 

24.1          23.8 

23.5 

23.2 

22.9 

22.6 

22.4 

22.1 

.5 

24.9 

23.6 

23.0 

22.7 

22.4 

22.2 

21.9 

21.6 

21.4 

21.1 

.6 

24.4 

23.1 

22.5          22.2 

22.0 

21.6 

21.4     i     21.2 

20.9 

20.7 

.8 

22.9 

21.7 

22.1 

20.8 

20.6 

20.3 

20.1          19.8 

19.6 

19.4 

2.0 

21.4 

20.3 

19.7 

19.5 

19.2 

19.0 

18.8 

18.5 

18.3 

18.1 

2.5 

19.0 

18  0 

17.6         17.3 

17.0 

16.9 

16.7         16.5 

16.3 

16.1 

3.0 

17-5 

16.6 

16.2 

16.0 

15.8 

15.6 

15.4 

15.2 

15.0 

14.8 

4.0 

15.7 

14.9 

14.5 

14.3 

14.1     !     13.9          13.8 

13.6 

13.4          13.3 

5.0 

14.4 

13.6 

13.3 

13.1          13.0     i     12.8          12.6 

12.5 

12.3     i     12.2 

6.0 

13.6 

12.9         12.5 

12.4     i     12  2         12.1          11.9 

11.8 

11.6     !     11.5 

7.0 

13.0 

12.3 

11.9 

11.8     !     11.7         11.5         11.4 

11.2          11.1          11.0 

8.0 

12.5 

11.8 

11.5 

11.4     :     11.2     i     11.1     ;     11.0 

10.8          10.7          10.6 

9.0 

12.0 

11.4 

11.1 

11.0     i     10.8 

10.7 

10.6 

10.4 

10.3          10.2 

10.0 

11.7 

11.1 

10.8 

10.7          10.6          10.4 

10.3 

10.2 

10.1          10.0 

11.0 

11.6 

10.9 

10.6 

10.4     i     10.3          10.2 

10.1 

10.0 

9.8            9.7 

12.0 

11.3 

10.7 

10.4 

10.3          10.1 

10.0 

9.9 

9.8 

9.6 

9.5 

13.0 

11.1 

10.5 

10.2 

10.1     i       9.9 

9.8 

9.7 

9  6            9.5            9.4 

14.0 

10.8 

10.3 

10.0 

9.9 

9.8 

9.6 

9.5 

9,4 

9.3           9.2 

16.0 

10.5 

10.0 

9.7 

9.6 

9.5           9.4 

9.3 

9.1 

9.0           8.9 

20.0 

10.0 

9.5 

9.3 

9.2 

9.0     |       8.9 

8.8 

8.7 

8.6 

8.5 

25.0 

9.6 

9.1 

8.9 

8.7 

8.6           8.5 

8.4 

8.3 

8.2 

8.1 

30.0           9.1 

8.8 

8.6 

8.5 

8.4            8.3 

8.2 

8.1             8.0 

7.9 

MEAN  TOTAL  PRESSURE  IN  POUNDS  PER  SQUARE  INCH  IN  NON-CONDUCTING 

CYLINDERS. 


No.  of 

Expan 

sions. 


INITIAL  PRESSURE  ABOVE  ATMOSPHERE. 

4d  60  80  100  120     i        141 


220 


.1 

14.9 

34.7 

54.5 

74.3 

94.1 

114 

134 

154 

193 

233 

.2 

14.7 

34.4 

54.1 

73.7 

93.4 

113 

133 

152 

192 

231 

.3 

14.5 

33.9 

53.4 

72.8 

92.1 

112 

131 

150 

189 

228 

.4 

14.2 

33.3 

52.4 

71.6 

9H.5 

109 

129 

148 

186 

224 

.5 

14.0 

32.6 

51.2 

69.7 

88.4 

107 

126 

144 

181 

219 

1.6 

13.7 

31.9 

50.2 

C8.4 

86.6 

105 

123 

141 

178 

214 

1.8 

13.0 

30.3 

47.6 

94.9 

82.2 

99.5 

117 

134 

169 

203 

2.0 

12.5 

29.2 

45.8 

63.9 

79.1 

95.8 

112 

126 

162 

196 

2.5 

11.2 

26.2 

41.2 

56.2 

71.2 

86.2 

101 

116 

146 

176 

3.0 

10.2 

23.7 

37.3 

50.9 

64.4 

78.0 

91-6 

105 

132 

159 

4.0 

8.5 

19.9 

31.2 

42.6 

54.0 

65-3 

76.7 

88.0 

111 

133 

5.0 

7.4 

17.3 

27.2 

37.1 

47.0 

56.9 

66.8 

76.7 

96.5 

116 

6.0 

6.6 

15.3 

24.0 

32.7 

41.5 

50-2 

58.9 

67.7 

85.1 

103 

7.0 

5.9 

13.7 

21.6 

30,1 

37.3 

46.2 

52.9 

60.8 

76.5 

92.2 

8.0  , 

5.3 

12.5 

19.6 

26.7 

33.9 

41.0  , 

48.1 

55.3 

69.5 

83  8 

9.0 

4.9 

11.5 

18.0 

24.6 

31.2 

37.7 

44.3 

50.9 

64.0 

77.1 

10.0 

4.6 

10.6 

16.7 

22.8 

28.8 

34.9 

41.0 

47.0 

59.2 

71.3 

11.0 

4.2 

10.1 

15.5 

21.2 

26.8 

32.5 

38.1 

43.8 

55.0 

66.4 

12.0 

4.0 

9.2 

14.5 

19.8 

25.0 

30.3 

35.6 

41.8 

51.0 

62.0 

13.0 

3.7 

8.7 

13.6 

18.6 

23.7 

29.2 

33.5 

38.4 

48.4 

58.3 

14.0 

3.5 

8.2 

12.9 

17.6 

22.3 

27.0 

31.7 

36.4 

45.8 

55,2 

16.0 

3.2 

7.4 

11.6 

15.9 

20.1 

24.3 

28.6 

32.8 

41.2 

49.7 

20.0 

2.7 

6.2 

9.8 

13.3 

16.8 

20.4 

23.9 

27.5 

34.5 

41.7 

25.11 

2.2 

5.2 

8  2 

11.1 

14.1 

17.1 

20.0 

23.  U 

28.9 

34.9 

30.0 

1.9 

4.5 

7_o 

y.o 

12.1 

14.7 

17.3 

19.8 

24.9 

30.0 

QUANTITY  OF  STEAM  USED,  ETC. 


67 


MEAN  EFFECTIVE  PRESSURE  IN   CONDENSING  ENGINES,  NON-CONDUCTING 

CYLINDERS. 


No.  of 
Expan- 
sions. 

INITIAL  PBESSUBE  ABOVE  ATMOSPHEBE,  IN  POUNDS 

PEE  SQUABE  INCH. 

0 

20 

i 

i 

60             80 

100 

120 

140 

180            220 

I 

1.1 
1.2 
1.3 
1.4 
1.5 
1.6 
1.8 
2.0 
2  5 
3.0 
4.0 
5.0 
6.0 
7.0 
8.0 
9.0 
10.0 
11.0 
12.0 
13.0 
14.0 
16.0 
20  0 
25.0 
30.0 

10.9 
10.7 
10.5 

10.2 
10.0 

9.7 
9.0 
8.5 
7.2 
6  2 
4.5 
3.4 
2.6 
1.9 
1.3 
0.9 
0.6 
0.2 
0 

30.7 
30.4 
29.9 
29.3 
28.6 
27.9 
26  3 
25.2 
22.2 
19.7 
15.9 
13.3 
11.3 
9.7 
8.5 
7.5 
6.6 
6-1 
5.2 
4.7 
4.2 
3.4 
2.2 
1.2 
0.5 

50.5 
50.1 
49.4 
48.4 
;     47.2 
46.2 
43.6 
41.8 
37.2 
33.3 
27.2 
23.2 
20.0 
17.6 
15.6 
14.0 
12.7 
11.5 
10.5 
9.6 
8.9 
7.6 
5.8 
4.2 
3.0 

70.3 
69.7 
68.8 
67.6 
65.7 
64.4 
60.9 
59.9 
52.2 
46.9 
38.6 
33.1 
28.7 
26.1 
22.7 
20.6 
18.8 
17.2 
15.8 
14.6 
13.6 
11.9 
9.3 
7.1 
5.6 

90.1 
89.4 
88.1 
86.5 
84.4 
82.6 
78.2 
75.1 
67.2 
60.4 
50.0 
43.0 
37.5 
33.3 
29.9 
27.2 
24.8 
22.8 
21.0 
19.7 
18.3 
16.1 
12.8 
10.1 
8.1 

110 
109 
108 
105 
103 
101 
95.5 
91.8 
82.2 
74.0 
61.3 
52.9 
46.2 
42.2 
37.0 
33.7 
30.9 
28.5 
26.3 
25.2 
23.0 
20.3 
16.4 
13.1 
lo.7 

130 
129 
127 
125 
122 
119 
113 
108 
97 
87.6 
72.7 
62.8 
54.9 
48.9 
44.1 
40.3 
37.0 
34.1 
31.6 
29.5 
27.7 
24.6 
19.9 
16.0 
13.3 

150 
148 
146 
144 
140 
137 
130 
122 
112 
101 
84.0 
72.7 
63.7 
56.8 
51.3 
46.9 
43.0 
39.8 
37.8 
34.4 
32.4 
28.8 
23.5 
19.0 
15.8 

189 
188 
185 
182 
177 
174 
165 
;  158 
142 
128 
107 
I     92.5 
81.1 
72.5 
65.5 
64.0 
55.2 
51.0 
47.0 
44.4 
41.8 
37.2 
30.5 
24.9 
20.9 

m 

227 
224 
220 
215 
210 
199 
192 
172 
155 
129 
112 
99 
88-2 
79.8 
73.1 
67.3 
62.4 
58.0 
54.3 
51.2 
45.7 
37.7 
30.9 
26.0 

MEAN  EFFECTIVE  PRESSURE,  IN  POUNDS  PER  SQUARE  INCH,  IN  NON- 
CONDENSING  ENGINES,  NON-CONDUCTING  CYLINDERS. 

No.  of 
Expan 
sions. 

INITIAL  PRESSURE  ABOVE  ATMOSPHEBE  IN 

POUNDS 

PEB  SQUABE  INCH. 

0 

20 

40 

60 

80 

100 

120 

140 

180            220 

.1 
.2 

.4 
.5 
1.6 
1.8 
2.0 
2.5 
3.0 
4.0 
5.0 
6.0 
7  0 
8.0 
9.0 
10.0 
11  0 
12.0 
13.0 
14.0 
16.0 
20.0 
25.0 
30.0 

16.7 
16.4 
15.9 
15.3 
14.6 
13.9 
12.3 
11.2 
8.2 
5.7 
1.9 

36.5 
36.1 
35.4 
34.4 
33.2 
32.2 
29.6 
27.8 
23.2 
19.3 
13.2 
9.2 
6.0 
3.6 
1.6 

: 

56.3 
55.7 
54.8 
53.6' 
51.7 
50.4 
46.9 
45.9 
38.2 
32.9 
24.6 
19.1 
14.7 
12.1 
8.7 
6.6 
4.8 
3.2 
1.8 
0.6 

76.1 
75.4 
74.1 
72.5 
70.4 
68.6 
64.6 
61.1 
53.2 
46.4 
36.0 
29.0 
23.5 
19.3 
15.9 
13.2 
10.8 
8.8 
7.0 
5.7 
4.3 
2.1 

96 
95 
94 
91 
89 
87 
81.5 
77.8 
68.2 
60.0 
47.3 
38.9 
32.2 
28.2 
23.0 
19.7 
16.9 
14.5 
12.3 
11.2 
9.0 
6.3 
2.4 

116 
115 
113 
111 
108 
105 
99 

73  6 
58-7 
48.8 
40.9     i 
34.9 
30.1 
26.3 
23.0 

15.5     \ 
13.7 
10.6 
5.9     ' 
2.0 

136 
134 
132 
130 
126 
123 
116        . 
108 
98 
87 
70.0 
5S.7 
49.7 
42.8 
37.3 
32.9 
19.0 
25.8 
23.8 
20.4 
18.4 
14.8 
9.5 
5.0 
1.8 

175 
174 
171 
168 
163 
160 
151 
144 
128 
114 
93 
78.5 
67.1 
58.5 
51.5 
46.0 
41.2 
27.0 
33.0 
30.4 
27.8 
23.2 
16.5 
10.9 
6.9 

215 
213 
210 
206 
201 
196 
185 
178 
158 
141 
115 
98 
85 
74.2 
65.8 
59.1 
53.3 
48.4 
44.0 
40.3 
37.2 
31.7 
23.7 
16.9 
12.0 



68  STEAM  r.s'/AV;,-   OH,  STEAK  ENGINE  PRACTICE. 


DATA  FURNISHED  BY  EXPERIMENT. 

In  comparing  the  accompanying  tables  with  the  performance  of  actual 
engines  the  back  pressure  may  be  found  to  vary  from  the  4  or  16  pounds 
per  square  inch  mentioned,  so  that  the  consumption  of  water  is  only 
tabulated  per  total  horse-power  at  present,  and  the  comparisons  made  on 
this  basis  are  not  affected  by  the  back  pressure. 

In  comparing  experiments  made  upon  the  performance  of  actual  en- 
gines, the  fact  must  not  be  forgotten  that  the  value  of  the  results  depend 
on  the  data  which  have  been  used  and  the  skill  of  the  experimenters; 
hence,  it  will  differ.  The  most  valuable  data  are  those  in  which  both  the 
heat  received  and  the  heat  rejected  by  the  engine  have  been  measured. 
These  require  measurements,  preferably  by  weight,  of  the  feed  water  fur- 
nished to  the  boiler,  the  pressure  and  temperature  of  evaporation,  and 
the  dryness  of  the  steam  near  the  engine;  the  work  done  in  the  cylinder, 
the  quantity  of  injection  water  and  its  rise  in  temperature;  the  difference 
between  the  heat  delivered  added  to  the  work  done  by  the  engine;  while 
the  heat  received  furnishes  an  important  check.  To  appreciate  the  value 
of  this  check  one  should  examine  some  of  the  first  experiments  in  which 
this  measurement  was  attempted,  and  which  may  be  found  in  the  Bulletin 
de  Societe'  Industrielle  de  Mulhouse  for  1857;  and  the  record  of  Hirn's  ex- 
periments show  the  difficulties  he  overcame. 

First,  reliable  experimental  data  can  only  be  obtained  from  Stationary 
Condensing  Engines,  on  account  of  the  impossibility  of  measuring  con- 
densing water:  the  difficulty  of  measuring  the  feed  water  precludes  the 
use  of  marine  engines  for  such  a  purpose. 

Next  in  point  of  value  are  experiments  where  the  heat  received  and 
delivered  are  carefully  ascertained,  either  by  measurements  of  the  feed  and 
priming,  or  the  water  of  condensation,  and  its  rise  in  temperature.  The 
latter  is  the  easiest  measurement  to  be  taken,  but,  for  the  most  reliable 
data  is  restricted  to  stationary  condensing  engines.  Measurements  of  feed 
water  and  priming  can  be  made  in  all  classes  of  engines,  with  the  excep- 
tion of  large  marine  engines  at  sea,  where  the  difficulty  of  getting  at  the 
quantity  of  feed  water  has  not  yet  been  overcome,  though  it  perhaps  might 
be  by  the  use  of  a  water  meter. 

Third  in  point  of  value  are  long- continued  experiments  made  on  en- 
gines in  which  the  feed  water  only  is  noted,  but  in  which  the  boilers  are  so 
large  that  the  priming  may  be  neglected.  Such  are  most  of  the  experi- 
ments made  by  the  United  States  Naval  authorities. 

Next  to  the  latter  in  point  of  scientific  value,  but  first  in  practical  in- 
terest, are  the  records  of  the  performances  of  the  large  ocean  steamships 
as  to  fuel  used  and  power  developed  in  long  voyages;  and  again,  the  records 
of  the  duty  of  pumping  engines.  In  such  records  it  is  impossible  to  sep- 
arate the  performances  of  engine  and  boiler,  but  the  results  are  compre- 
hensive and  of  great  value. 

Last  in  point  of  value  are  short  experiments  in  which  the  fuel  or  the 
feed-water  is  measured,  in  some  indirect  manner,  and  the  engine  "indi- 
cated" only,  as,  of  course  it  must  be. 


We  give,  in  the  following  table,  some  engine  trials  made  by  various 
authorities,  classing  them  under  the  three  first  summaries  of  value  given 
above,  as  A,  B  and  C.  This  table  might  be  greatly  extended,  but  only  by 
the  admission  of  experiments  which  are  either  isolated,  improbable,  or 
deficient  in  the  required  data. 

A  very  casual  examination  of  the  table  shows  us  that  economy  of 
steam  is  promoted  by  high  pressure  and  high  speed,  while  the  cost  in 
steam  of  a  total  horse-power  is  lessened  by  large  expansion,  and  the  cost 
of  a  net  horse-power  is  least  with  moderate  expansion. 

Another  fact  brought  prominently  to  the  front  is  that  the  actual  use  of 
steam  is  very  far  in  excess  of  that  given  by  our  tables  for  a  non-conduct- 
ing cylinder.  This  excess  is  due  to  several  causes: 

1.  To  the  use  of  wet  steam. 

2.  To  the  loss  by  clearance  space. 

3.  To  external  radiation  and  loss  of  heat. 

4.  To  internal  radiation  and  the  transfer  of  heat  between  the  iron  of 
the  cylinder  and  its  contained  steam. 

For  our  purpose  we  shall  not  individually  consider  these  four  causes 
of  loss,  but  we  may  take  up  our  table  of  experimental  data  and  compute 
from  the  tables  already  given  the  amount  of  steam  that  would  be  used  by 
a  non-conducting  cylinder,  working  with  steam  of  the  same  initial 
pressure  and  expansion.  Deducting  this  quantity  from  the  quantity 
actually  used  we  will  examine  the  excess  to  ascertain  what  law,  if  any,  can 
be  found  to  account  for  it. 


70 


STEAM  USING;  Off,  STEAM  ENGINE  PRACTICE. 


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74 


XTKAM 


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'./TAXTITY  OF  STEAM  USED,  ETC. 


75 


SINGLE  UN  JACKETED   CYLINDERS. 

To  continue  our  investigation,  we  may  set  forth  our  results,  obtained 
from  the  foregoing  table,  as  follows: 

U.  S.  S.  S.  "MICHIGAN." 


Steam  used  in  Non- 
Steam  used  per  to-     conducting  Cylin- 
tal  horse-power  per     der  per  tot'l  horse- 
hour,  power  per  hour. 


35 

30.9 

29.4 

30.6 

29.8 

30.7 

32.0 


Excess  per  total 

horse-power 

per  hour. 


23.3 
20.0 
16.3 
15.4 
13.5 
11.7 


6 

7.6 
9.4 
14.3 
14.4 
17.2 
20.3 


Excess  per  hour 
used. 


2,065 
1,709 
2,160 
2,200 
2,071 
1,552 
1,782 


-T-  7  =  1,934  ponuds,  mean. 


13,539 


The  excess  found  clearly  follows  no  law  connected  with  the  expansion, 
and  we  shall  hereafter  be  justified  in  taking  the  mean  value  as  that  to  be 
followed. 

U.  S.  B.  S.  "DALLAS." 


Steam  used  per  to- 
tal horse-power  per 
hour. 

Steam  used  in  Non- 
conducting Cylin- 
der per  tot'l  horse- 
power per  hour. 

Excess  per  total 
horse-power 
per  hour. 

Excess  per 
used. 

hour 

8                  23.0 
9                  23.3 
10                 23.1 
11                  24.8 
12                 26.5 

13.2 
16.0 
16.2 
16.3 
19.5 

9.8 
7.3 
6.9 
8  5 
7.0 

1,562 

1,584 
1,778 
2,400 
1,935 

9,259  -i-  5  =  1,852  pounds,  mean. 


9,259 


U.  S.  R.  S.  "DEXTER.1 


21.7 
21.9 
21.8 
21.6 


13.6 
14.7 
15.0 
16.4 


8.1 
7.2 
6.8 
5.2 


-f-  4  =  1,650  pounds,  mean. 


25.6 
25.9 
28.2 


15.9 
18.0 
19.7 


9.7 
7.9 


4,660  -i-  3  =  1,553  pounds,  mean. 


1,360 
1.430 
1,870 

4,660 


76 


STEAM  USING;  OR,  STEAM  ENGINE  PRACT WE. 


SINGLE   UNJACKETED    CYLINDEKS.—  Continued. 
U.  S.  R.  S.  "GALLATIN." 


Steam  used  in  Non- 

Steam  used  per  to-     conducting  Cylin-     Excess  per  total         Excess  per  hour 
tal  horse-power  per;    der  per  tot'l  horse-         horse-power                      used, 
hour.                              power  per  hour.                 per  hour. 

1 

19.2 

13.8 

5.4 

1,430 

19  4 

15.1 

4.3 

1,330 

21.2 

17.2                                  4.0 

1,420 

4,180  -T-  3  =  1,393  pounds,  mean. 

4,180 

23 

19.8 

13.1                                  6.7 

2,120 

24 

20.5 

14.3 

6.2 

1,990- 

25 

21.5 

13.6 

7.9                                       2,410 

26 

21.3 

11.3 

10.0                                       2,170 

27 

20.6 

12.4 

8.2 

2,200 

28 

19.6 

13.1 

6.5 

2,030 

29 

21.5 

14.0 

7.5 

2,360 

15,280  -±  7  =  2,183  pounds,  mean. 

15,280 

00 

22.4 

12.5                                       9.9 

1,450 

31 

23.0 

13.2                                       9.8 

1,440 

32 

21.3 

14.9 

6.4 

1,310 

33 

21.8 

16.9 

4.9 

1,310 

34 

23.4 

18.7                                       4.7 

1,340 

6,850  -r  5  —  1,370  pounds,  mean. 

6,850 

MILLERS'  EXHIBITION  AT  CINCINNATI. 

35 
36 
37 

1      - 

11.5 

5.6 

1,058 

40 
41 
42 
43 
44! 


17.24 
18.61 


36.4 
29.2 
31.1 
32.1 
30.3 


HIRN'S  ENGINE. 


11.8 
14.4 


5.4 
4.2 


1,310  -r-  2  =  655  pounds,  mean. 
This  will  be  increased  on  account  of  the 
French  units   used,  and  will   equal   733 
pounds,  mean. 


U.  S.  S.  "EUTAW." 


15.4 
17.5 
21.5 
21.6 
23.0 


21.0 
11.7 

9.6 
10.5 

7.5 


16,670  -f-  5  =  3,337  pounds,  mean. 


650 
660 


1.310 


3,520 
2,810 
3,760 
3,370 
3,210 

16,670 


HIGH  SERVICE  PUMPING  ENGINE,  NO.  1,  ST.  LOUIS  WATER  WORKS. 
1  |  15.3  4.3  4,120 

MASSACHUSETTS  INSTITUTE  OF  TECHNOLOGY. 


46                  2  ,  .  7 

14.4 

13.3 

173 

47 

29.0 

19.6 

9.5 

175 

48 

33.5 

24.0 

9.5 

197 

545  -4-  3  =  182  r 

ounds.  mean. 

545 

QUA  XT/TV  <>r  STA'.I.V  1'SED,  ETC.  77 


It  will  be  observed  that  we  have  summed  up  the  experiments,  made 
at  the  Millers'  Exhibition,  at  Cincinnati,  on  three  different  competing 
engines.  These  showed  so  little  difference  that  the  results  of  our  investi- 
gation on  one  may  be  taken  to  represent  the  three. 

We  have  also  summed  up  the  following  data  from  the  table: 

U.  S.  STEAMER  "MICHIGAN." — Seven  experiments:  Cylinder 
36"  x  96".  Initial  steam  pressure,  20  Ibs.  above  atmosphere. 
Back  pressure,  say  5  Ibs.,  equal  to  10  Ibs.  below  atmosphere. 
Mean  excess  of 'water  per  hour  over  that  required  in  a  non- 
conducting cylinder 1,934  Ibs. 

U.  S.  KEVENUE  STEAMER  "DALLAS." — Six  experiments:  Cylin- 
der 36"  x  30".  Initial  steam  pressure,  say  30  Ibs.  above 
atmosphere.  Mean  back  pressure,  say  5  Ibs.  above  zero. 
Mean  excess  of  water  per  hour  above  that  required  by  a 
non-conducting  cylinder 1,852  Ibs. 

U.  S.  KEVENUE  STEAMER  "DEXTER." — Four  experiments:  Cylin- 
der 26"  x  30".  Mean  back  pressure,  say,  5  Ibs.  above  zero. 
Initial  steam  pressure  above  atmosphere,  68  Ibs.  Excess  of 
water  per  hour  above  that  required  by  a  non  conducting 
cylinder '. 1,650  Ibs. 

Three  experiments:  Cylinder  26"  x  30"  Mean  back  pressure, 
say,  5  Ibs.  above  zero.  Initial  steam  pressure  above  atmos- 
phere, 40  Ibs.  Excess  of  water  per  hour  above  that  required 
by  a  non-conducting  cylinder 1,553  Ibs. 

U.  S.  KEVENUE  STEAMER  "GALLATIN." — Mean  of  seven  experi- 
ments: Cylinder  34.1"  x  30".  Mean  back  pressure,  say,  5 
Ibs.  above  zero.  Initial  steam  pressure  70  Ibs.  above  atmos- 
phere. Excess  of  water  per  hour  above  that  required  by  a 
non-conducting  cylinder 2,183  Ibs. 

Mean  of  five  experiments:  Cylinder  34.1"  x  30".  Mean  back 
pressure,  say,  5  Ibs.  above  zero.  Initial  steam  pressure  40 
Ibs.  above  atmosphere.  Excess  of  water  per  hour  above 
that  required  by  a  non-conducting  cylinder 1,370  Ibs. 

Mean  of  three  experiments:  Cylinder  34.1"  x  30".  Mean  back 
pressure,  2  Ibs.  above  atmosphere.  Initial  steam  pressure,, 
70  Ibs.  above  atmosphere.  Excess  of  water  per  hour  above 
that  required  by  a  non-conducting  cylinder 1,393  Ibs. 

MILLER'S  EXHIBITION  AT  CINCINNATI. — Mean  of  three  engines: 
Cylinder  18"  x  48".  Initial  steam  pressure,  above  atmos- 
phere, 82  Ibs.  Mean  back  pressure,  say  4  Ibs.  Excess  of 
water  per  hour  above  that  required  by  a  non-conducting 
cylinder 1,058  Ibs. 


78  STEAM  USING;  07?,  STEAM  ENGINE  PRACTICE. 

HIBN'S  ENGINE.— Mean  of  two  experiments:  Cylinder  24"  x 
78".  Initial  steam  pressure  above  atmosphere  54  Ibs.  Mean 
back  pressure,  2  Ibs.  Excess  of  water,  per  hour,  above  that 
required  by  a  non-conducting  cylinder 733  Ibs. 

U.  S.  STEAMEB  "EUTAW." — Mean  of  five  experiments:  Cylinder 
58"  x  105".  Initial  steam  pressure,  25  Ibs.  above  atmos- 
phere. Mean  back  pressure,  4  Ibs.  Excess  of  water,  per 
hour,  above  that  required  by  a  non-conducting  cylinder. . .  3,337  Ibs. 

MASSACHUSETTS  INSTITUTE  or  TECHNOLOGY. — Mean  of  three 
experiments  with  Corliss  engine:  Cylinder  8"  x  24".  Initial 
steam  pressure,  50  Ibs.  above  atmosphere.  Excess  of  water 
per  hour  above  that  required  by  a  non-conducting  cylinder.  182  Ibs. 

HIGH  SEBVICE  PUMPING  ENGINE,  No.  1,  ST.  Louis  WATEE 
WOBKS.— One  experiment:  Cylinder  85"  x  120".  Initial 
steam  pressure,  40  Ibs.  above  atmosphere.  Excess  of  water 
per  hour  above  that  required  by  a  non-conducting  cyl- 
inder   4,120  Ibs. 

Of  the  four  causes  of  excess  in  steam  used  over  that  required  by  a 
non-conducting  cylinder,  which  we  have  already  mentioned,  the  first  or 
that  of  steam  entering  with  water  caused  by  foaming  or  priming,  we  shall 
neglect  here,  as,  in  some  of  our  experiments,  to -wit,  the  last  two,  this  has 
been  eliminated,  and  in  others  can  scarcely  be  very  large.  The  third,  or 
that  of  external  radiation,  is  usually  very  small  and  can  not  exceed  that  of 
a  steam-heating  coil  of  the  same  area  as  the  external  surface  of  the  cylin- 
der. The  second  is  a  loss  which  may,  in  determining  the  cost  of  a  total 
horse-power,  be  considered  to  vary  with  the  volume  of  clearance  space, 
but  which  ranges  from  less  than  1  to  15  per  cent,  of  the  piston  displace- 
ment, and  is,  on  an  average,  about  8  per  cent,  thereof.  This,  in  a  cylinder 
full  of  steam  at  the  terminal  pressure,  is  not  a  great  loss  in  itself,  but 
there  is  a  loss  during  the  expansion  also.  In  any  case  it  is  not  large  com- 
paratively, is  nearly  proportional  to  the  volume,  and,  consequently,  varies 
with  the  piston  area  and  a  percentage  of  the  stroke. 

The  fourth  source  of  loss  is  by  far  the  largest,  and  is  due  to  an  action 
first  mentioned  by  D.  K.  Clark  in  his  "Eailway  Machinery, "  in  1851,  and 
afterwards  elaborated  by  M.  G.  A.  Him,  in  1854  and  again  in  1857,  in  the 
Bulletins  de  la  Societe  Industrielle  de  Mulhouse,  and  therein  repeated  at 
frequent  intervals  up  to  the  present  date.  This  action  was  subsequently 
noted  by  Isherwood  in  the  second  volume  of  his  "Experimental  Kesearches 
in  Steam  Engineering,"  and  it  was  rediscovered  by  Mr.  G.  B.  Dixwell,  of 
Boston,  and  communicated  by  him  to  the  Society  of  Arts  of  that  city. 

The  internal  radiation,  or  the  action  of  the  internal  surfaces  of  the  cyl- 
inder upon  the  within  contained  steam,  may  be  explained  as  follows: 
Steam  enters  the  cylinder  from  the  boiler  at  ,a  temperature  corresponding 


QUANTITY  OF  STEAM  USED,  ETC.  79 


to  the  pressure,  and  leaves  the  cylinder  at  a  lower  temperature  correspond- 
ing to  the  lower  pressure.  The  metal  of  the  cylinder  being  a  very  good  con- 
ductor of  heat,  receives  heat  from  the  incoming  and  delivers  heat  to  the 
outgoing  steam  at  every  revolution.  In  detail  the  action  is  thus:  When 
the  steam-valve  opens  there  is  admitted  from  the  boiler  hot  steam  which 
first  fills  the  clearance  space,  coming  in  contact  with  the  cool  surfaces 
which  have  just  been  open  to  the  exhaust  surfaces,  and  which  are  from 
100°  to  200°  Fahr.  lower  in  temperature  than  the  incoming  steam.  The 
amount  in  weight  of  the  steam  is  small  and  the  amount  in  surface  of 
the  enclosing  metal  being  large,  the  result  is  naturally  that  the  steam  con- 
denses until  heat  enough  has  been  given  to  the  metal  to  raise  its  surface 
to  the  temperature  of  the  steam.  The  piston  moves  and  the  condensation 
continues  up  to  the  cut-off.  During  the  expansion,  as  the  pressure  falls, 
the  warmed  surface  begins  to  give  out  heat  to  the  steam  as  the  pressure 
and  temperature  of  the  steam  fall,  while,  as  the  piston  moves,  the  metal 
which  has  been  exposed  to  the  exhaust  is  opened  to  the  steam  and  the  ac- 
tion is  the  reverse  of  that  going  on  at  other  portions  of  the  surface,  while 
during  exhaust  the  action  continues  to  transfer  heat  from  the  metal  to  the 
steam  which  is  swept  out  of  the  cylinder. 

There  is  experimental  reason  to  believe  that  the  temperature  of  what 
may  be  called  the  skin  of  the  metal  scarcely  varies  from  that  of  the  steam, 
while  the  depth  to  whjch  the  influence  extends,  or  what  may  be  called  the 
thickness  of  this  skin,  depends  upon  the  intensity  and  rapidity  of  the 
changes  of  temperature  to  which  it  is  subjected. 

The  experimental  evidence  is  as  follows:  A  metallic  pyrometer  must 
be  so  made  that  a  thin  sheet  of  metal  can  be  exposed  to  the  steam  in  the 
cylinder,  or  connected  to  the  indicator  fittings,  having  a  needle  so  adjusted 
and  arranged  as  to  show  changes  of  length  in  the  sheet  of  metal.  The 
instrument  must  be  rated  by  exposure  to  steam  free  from  air  at  atmos- 
pheric pressure  and  to  water  of  a  known  temperature.  On  exposing  such 
an  instrument  to  the  action  of  the  steam  in  the  cylinder,  a  change  of  tem- 
perature will  be  noted  at  each  stroke. 

If  the  shell  be  made  of  iron  0.03  inch  thick,  and  the  piston  have  a 
speed  due  to  60  revolutions  of  the  crank  per  minute,  nearly  the  whole 
change  of  temperature  due  to  the  change  in  pressure,  and  the  needle,  will 
remain  stationary  during  nine -tenths  of  the  exhaust  stroke. 

If  the  instrument  be  filled  with  mercury  so  that  heat  may  be  trans- 
mitted to  the  interior  through  the  skin,  while  the  freedom  of  movement 
of  the  skin,  by  which  alone  the  change  of  temperature  can  be  observed, 
is  not  interfered  with,  at  a  piston  speed  due  to  85  revolutions  per  minute, 
the  same  change  has  been  observed  in  the  action  of  the  instrument  as  be- 
fore the  introduction  of  the  mercury. 

If  the  number  of  revolutions  per  minute  be  increased  beyond,  say  100, 
the  indications  of  the  instrument  decrease,  and  are,  approximately,  in- 
versely proportional  to  the  number  of  revolutions. 

The  problem  of  the  transfer  of  heat  to  and  from  the  steam,  in  an  en- 
gine cylinder,  although  complex,  is  probably  within  the  compass  of  pure 


80  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


mathematics,  but  we  shall  not  attempt  to  analyse  it  here,  for  it  would  be 
foreign  to  the  spirit  of  this  work. 

The  fourth  loss  might  be  considered  to  be  proportional  to:  1.  The 
whole  internal  surface  of  the  cylinder:  2.  To  the  area  of  the  cylinder 
and  piston  heads  and  a  fraction  of  the  barrel:  3.  To  the  area  of  the  piston: 
and,  4.  To  the  diameter  of  piston.  It  may  also  be  considered  to  vary  with 
the  difference  of  temperature  between  initial  pressure  and  that  of  the 
condenser  or  exhaust  pipe. 

A  careful  examination  of  the  table  of  experiments  shows:  that  neglect- 
ing priming  and  external  radiation  the  whole  excess  of  water  used  per 
hour  over  that  required  in  a  non-conducting  cylinder  is  rudely  propor- 
tional to  the  difference  of  temperature  between  the  incoming  and  outgoing 
steam,  and  to  the  diameter  of  the  piston;  and  that  such  excess  is  nearly 
constant  for  the  great  range  of  piston  speed  and  revolutions  therein 
found,  and  moreover  is  entirely  independent  of  the  expansion. 

We  give  some  of  the  figures  connected  with  the  experiments  in  refer- 
ence to  the  above  points: 

TJ.   S.    STEAMER   "MICHIGAN." 

Seven  experiments.  Diameter  of  piston,  3  feet.  Excess  of  water  in 
pounds  per  hour  over  that  required  by  a  non-conducting  cylinder  =  1,934. 

Temperature  of  steam 259° 

Temperature  of  condenser 104° 

259°  —  104°  =  155°  =  change  of  temperature: 

155°  x  3  =  diameter  of  piston  =  465  =  product  of  change  of  temperature  x 
diameter  of  piston.  1,934  -=-  465  =  4  16  =  pounds  of  water  in  excess  per 
hour,  per  foot  diameter  of  piston,  per  degree  Fahr.  of  change  in  tem- 
perature. 

TJ.    S.    STEAMER   "DALLAS." 

Diameter  of  piston,  3  feet.  Excess  of  water  in  pounds  per  hour  over 
that  required  by  a  non-conducting  cylinder  =  1,852. 

Temperature  of  steam 274° 

Temperature  of  condenser 104° 

274  —  104  =  170°  =  change  of  temperature: 

170  x  3  =  510  =  product  of  change  of  temperature  x  diameter  of  piston. 
1,852  -f-  510  =  3.63  =  pounds  of  water  in  excess  per  hour,  per  foot  diameter 
of  piston,  per  degree  Fahr.  of  change  of  temperature. 

U.    S.    STEAMER   "DEXTER." 

Diameter  of  piston  2.17  feet.  Excess  of  water  in  pounds  per  hour 
over  that  required  by  a  non-conducting  cylinder  =  1,650. 

Temperature  of  steam 315° 

Temperature  of  condenser 104° 

315  —  104  =  211°  =  change  of  temperature: 

211  x  2.17  =  say  458  =  product  of  change  of  temperature  x  diameter  of 
piston.  1,650  -=-  458  =  3.60  =  pounds  of  water  in  excess  per  hour,  per  foot 
of  piston  diameter,  per  degree  Fahr.  of  change  of  temperature. 


QUANTITY  OF  STEAM  USED,  ETC.  81 

Excess  of  water  in  pounds  per  hour  over  that  required  by  a  non- 
conducting cylinder  =  1,553. 

Temperature  of  steam 287° 

Temperature  of  condenser 104° 

287  —  104  =  183°  =  change  of  temperature: 

183  x  2.17  =  397  =  product  of  change  of  temperature  x  diameter  of  pis- 
ton. 1,553  -4-  397  =  3.91  =  pounds  of  water  in  excess  per  hour,  per  foot 
diameter  of  piston,  per  degree  Fahr.  of  change  of  temperature. 

U.   S.   REVENUE   STEAMER   "GALLATIN." 

Mean  of  seven  experiments:  Diameter  of  piston  2.84  feet.  Excess  of 
water  in  pounds  per  hour  over  that  required  by  a  non-conducting  cylin- 
der =  2,183. 

Temperature  of  steam 316° 

Temperature  of  condenser 104° 

316  —  104  =  212°  =  change  of  temperature: 

212  X  2.84  =  say  602  =  product  of  change  of  temperature  x  diameter  of 
piston.  2,183  -4-  602  =  3.62  =  pounds  of  water  in  excess  per  hour,  per  foot 
diameter  of  piston,  per  degree  Fahr.  of  change  of  temperature. 

Mean  of  five  experiments:  Excess  of  water  in  pounds  per  hour  over 
that  required  by  a  non-conducting  cylinder  =  1,427. 

Temperature  of  steam 287° 

Temperature  of  condenser 104° 

287  —  104  =  183°  =  change  of  temperature: 

183  x  2.84  =  say  520  =  product  of  change  of  temperature  x  diameter  of 
piston.  1,370  -=-  520  =  2.63  =  pounds  of  water  in  excess  per  hour,  per  foot 
diameter  of  piston,  per  degree  Fahr.  of  change  of  temperature. 

Mean  of  three  experiments:  Excess  of  water  in  pounds  per  hour  over 
that  required  by  a  non-conducting  cylinder  =  1,380. 

Temperature  of  steam 316° 

Temperature  of  condenser 212° 

316  —  212  =  104°  =  change  of  temperature: 

104  x  2.84  =  295  =  product  of  change  of  temperature  x  diameter  of  piston. 
1,393  -=-  295  =  4.72  =  pounds  of  water  in  excess  per  hour,  per  foot  diometer 
of  piston,  per  degree  Fahr.  of  change  of  temperature. 

MILLER'S  EXHIBITION  AT  CINCINNATI. 

Mean  of  three  engines:  Diameter  of  piston  1.5  feet.  Excess  of  water 
in  pounds  per  hour  over  that  required  by  a  non-conducting  cylinder  = 
1,058. 

Temperature  of  steam 326° 

Temperature  of  condenser 104° 

326  —  104  =  222°  =  change  of  temperature: 

222  x  1.5  =  333  =  product  of  change  of  temperature  x  diameter  of  piston. 
1,058  -f-  333  =  3.17  =  pounds  of  water  in  excess  per  hour,  per  foot  diameter 
of  piston,  per  degree  Fahr.  of  change  of  temperature. 


82  STEAM  rSING;  OR,  STEAM  E\<;1XK  PRACTICE. 


HIKN'S  ENGINE. 

Diameter  of  piston  2  feet.    Excess  of  water  in  pounds  per  hour  over 
that  required  by  a  non-conducting  cylinder  =  733. 

Temperature  of  steam , 302° 

Temperature  of  condenser 104° 

302  —  104  —  198°  =  change  of  temperature: 

198  x  2  =  396  =  product  of  change  of  temperature  x  diameter  of  piston. 
733  -4-  396  =  1.85  =  pounds  of  water  in  excess  per  hour,  per  foot  diame- 
ter of  piston,  per  degree  Fahr.  of  change  of  temperature. 

U.    S.    STEAMEK   "EUTAW." 

Diameter  of  piston  =  4.83  feet.    Excess  of  water  in  pounds  per  hour 
over  that  required  by  a  non-conducting  cylinder  —  3,334. 

Temperature  of  steam 267° 

Temperature  of  condenser 104° 

267  —  104  =  163°  =  change  of  temperature: 

163  x  4.83  =  787  =  product  of  change  of  temperature  x  diameter  of  piston. 
3,337  -r-  787  =  4.24  =  pounds  of  water  in  excess  per  hour,  per  foot  diame- 
ter of  piston,  per  degree  Fahr.  of  change  of  temperature. 

MASSACHUSETTS   INSTITUTE   OF   TECHNOLOGY. 

Diameter  of  piston  =  0.67  foot.    Excess  of  water  in  pounds  per  hour 
over  that  required  by  a  non-conducting  cylinder  =  182. 

Temperature  of  steam 298° 

Temperature  of  condenser 212° 

298  —  212  =  86°  =  change  of  temperature: 

86  x  0.67  =  58  =  product  of  change  of  temperature  x  diameter  of  piston. 
182  ~-  58  =  3.14  =  pounds  of  water  in  excess  per  hour,  per  foot  diameter 
of  piston,  per  degree  Fahr.  of  change  of  temperature. 

HIGH   SEBVICE  PUMPING  ENGINE,   NO.  1,   ST.  LOUIS   WATER  WORKS. 

Diameter  of  piston  =  7.08  feet.    Excess  of  water  in  pounds  per  hour 
over  that  required  by  a  non-conducting  cylinder  =  4,120. 

Temperature  of  steam 287° 

Temperature  of  condenser ^20° 

287  —  120  =  167°  =  change  of  temperature. 

167  x  7.08  =  1,182  =  product  of  change  of  temperature  x  diameter  of  pis- 
ton. 4,120  -f-  1.182  =  3.48  —  pounds  of  water  in  excess  per  hour,  per  foot 
diameter  of  piston,  per  degree  Fahr.  of  change  of  temperature. 


QUANTITY  OF  STEAM  USED,  ETC. 


83 


SUMMARY. 


IL 

If 


LOCATION. 


20 

36 

7 

U.  S.  Steamer  "Michigan"    ..   .. 

4  16 

29  12 

30 

36 

6 

U.  S.  Steamer  "Dallas"  

3.63 

21.78 

70 

26 

4 

U.  S.  Steamer  "Dexter" 

3.60 

14  40 

40 

3 

3  91 

11  73 

70 

34 

U.  S  Steamer  "Gallatin" 

3  62 

25.34 

40 

5 

2.63 

13.15 

70 

no  vacuum 

3 

m  •            m                         n 

4.72 

14.16 

25 

58 

5 

U.  S.  Steamer  "Eutaw" 

4  24 

21  20 

80 

18 

3 

Miller's  Exhibition  

3.17 

9.51 

40 
54 

85 
24 

1 
9 

St.  Louis  Water  Works,  No.  1  H.  S.  . 
Him  

3.48 
1  85 

3.48 
3.70 

50 

8 

3 

Mass.  Institute  Technology  

3.14 

9.42 

49 

176.99 

176.99  -r-  49  =  say  3.6  =  mean  pounds  of  water  in  excess  per  hour,  per 
foot  of  piston  diameter,  per  degree  Fahr.  difference  of  temperature. 

In  the  49  experiments,  above  recorded,  we  find  a  certain  variation  in 
the  resulting  excess  per  foot  of  piston  diameter  per  degree  of  change  of 
temperature,  but  in  connection  with  this  we  must  remember  that  we  have 
not  taken  into  account  the  difference  of  clearance  between  the  different 
engines.  For  instance,  the  lowest  value  given  above  is  that  for  Hirn's 
engine,  and  this  has  the  least  clearance,  while  the  condition  of  the  steam 
and  the  amount  of  cushion  are  in  all  the  cases  neglected.  Furthermore, 
while  the  results  are  widely  different,  yet  the  error  in  per  cent,  of  the 
whole  steam  used  is  a  much  smaller  one,  and  we  shall  find  that  adding  to 
the  steam  used  in  a  non-conducting  cylinder  the  excess  found  above,  we 
shall  arrive  at  a  close  approximation  to  the  steam  actually  used. 

When  we  examine  the  cases  of  single -jacketed  cylinders,  we  find,  as  a 
whole,  a  less  excess  in  the  use  of  steam  above  that  used  in  a  non-conduct- 
ing cylinder,  but  the  gain  so  made  does  not  appear  to  be  reduced  to  any 
such  simple  law  as  that  found  for  unjacketed  engines,  and,  in  fact,  the  use 
of  larger  expansion,  and  consequent  loss  by  back  pressure  work,  very 
often  neutralizes  the  gain  achieved. 

The  compound  engines,  in  our  table,  give  very  little  better  results 
than  the  simple  engines,  with  the  same  steam  pressures  and  expansions,  in 
the  cost  of  steam  per  total  horse  power;  while  per  net  horse  power  the 
larger  amount  of  back  pressure  work,  and  the  actual  friction  of  two  pis- 
tons, with  their  rods  and  set-off  connections,  go  very  far  to  neutralize  any 
very  great  gain  in  such  types. 


84  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

We  find  that  the  data  are  not  sufficient  to  give  an  empirical  formula 
for  the  excess  of  water  over  that  used  in  a  non-conducting  cylinder;  but 
we  see  that  it  is  not  very  far  from  that  of  a  single-jacketed  cylinder  of  the 
same  size  as  the  large  one.  We  are  obliged,  therefore,  to  await  further 
experiments. 

We  do  not  claim,  even,  for  the  single  un jacketed  cylinder  that  our 
method  of  investigation  is  either  final,  exhaustive,  or  rational,  but  that 
the  results  are  all  that  our  present  knowledge  of  the  subject  will  give  us, 
will,  we  think,  be  admitted.  What  is  required  is  a  great  number  of 
experiments  under  the  conditions  of  class  A,  upon  all  kinds  and  sizes  of 
engines;  we  can  then  hope  to  frame  a  much  more  accurate  and  rational 
theory  than  the  crude  one  we  have  given. 

We  add  a  few  tables,  the  application  of  which  will  be  readily  seen. 


NUMBER  OF  POUNDS  OF  WATER  USED  PER  SQUARE  FOOT  OF  PISTON  PER 
HOUR,  FOR  A  PISTON  SPEED  OF  ONE  FOOT  PER  MINUTE  IN  A  NON- 
CONDUCTING CYLINDER. 


INITIAL  PEESSUBE  IN  POUNDS  PEE  SQUAEE  INCH  ABOVE  ATMOSPHEEE. 


No.  of 

Expan- 
sions. 

0 

20 

40 

60 

80 

100 

120 

140 

180 

220 

1.1 

2.12 

4.69 

7.35 

9.66 

12.1 

14.4 

16.8 

19.0 

23.6 

28.2 

1.2 

.92 

4.30 

6.64 

8.86 

11-  1 

13.2 

15.4 

17.4 

21.6 

32.5 

1.3 

.75 

3.88 

5.93 

7.99 

9.99 

11.9 

13.9 

15.7 

19.5 

23.3 

1.4 

.63 

3.60 

5.51 

7.42 

S.28 

11.1 

12.9 

14.6 

18.1 

21.6 

1.5 

.52 

3.36 

5.14 

6.91 

8.66 

10.4 

12.0 

13.6 

16.9 

20.2 

1.6 

.46 

3.22 

4.93 

6.64 

8.31 

9.91 

11.5 

13.1 

16.2 

19.3 

1.8 

.30 

2.86 

4.38 

5.90 

7.38 

8.83 

10.2 

11.6 

14.4 

17.2 

2.0 

.17 

2.58 

3.95 

5.44 

6.65 

7.95 

9.21 

10.5 

13.3 

15.5 

2.5 

0.933 

2.06 

3.16 

4.25 

5.29 

6.36 

7.37 

8.36 

10  4 

12.4 

3.0 

0.777 

1.72 

2.63 

3.54 

4.43 

5.30 

6.14 

6.97 

8.66 

10.3 

4.0 

0.583 

1.26 

1.97 

2.66 

3.32 

3.97 

4.58 

5.23 

6.49 

7.74 

5.0 

0.466 

1.03 

1.58 

2.17 

2.66 

3.19 

3.69 

4.18 

4.96 

6  19 

6.0 

0.389 

0.859 

1.32 

1.77 

2.07 

2.65 

3.07 

3.48 

4.32 

5.16 

7.0 

0.333 

0.736 

1.12 

1.55 

1.90 

2.32 

2.63 

2.99 

3.71 

4.42 

8.0 

0.292 

0.644 

0.987 

1.33 

1.66 

1.98 

2.30 

2.61 

3.25 

3.87 

9.0 

0.258 

0.571 

0.875 

1.18 

1.47 

1.76 

2.04 

2.32 

2.88 

3.43 

10.0 

0.233 

0.516 

0.789 

1.06 

1.33 

1.59 

1.84 

2-09 

2.60 

3.09 

11.0 

0.212 

0.235 

0.717 

0.966 

1.21 

1.44 

1.68 

1.90 

2.36 

2.81 

12.0 

0.194 

0.430 

0.658 

0.886 

1.11 

1.32 

1.54 

1.78 

2.16 

2.58 

13.0 

0.180 

0.397 

0.593 

0.818 

1.03 

1.25 

1.39 

1.61 

2.00 

2.38 

14.0 

0.167 

0.369 

0.564 

0.759 

0.949 

1.14 

1.32 

1.49 

1.85 

2.21 

16.0 

0.146 

0.322 

0.494 

0.664 

0.831 

0.993 

1.15 

1.31 

1.62 

1.93 

20.0 

0.117 

0.258 

0.395 

0.531 

0.665 

0.775 

0.921 

1.04 

1.30 

1.54 

25.0 

0.0933 

0.206 

0.316 

0.425 

0.532 

0.636 

0.737 

0.836 

1.04 

1.21 

30.0 

0.0777 

0.172 

0.263 

0.354 

0.443 

0.526 

0.587 

0.697 

0.866 

1.03 

QUANTITY  OF  STEAM  USED,  ETC. 


85 


NUMBER  OF  TOTAL  HORSE-POWER  FOR  EACH  CUBIC  FOOT  OF  SPACE 
SWEPT  BY  PISTON  PER  MINUTE. 


INITIAL  PBESSUBE  IN  POUNDS  PEE  SQUABE  INCH  ABOVE  ATMOSPHEBE. 


No.  of 

Expan- 
sions. 

0 

20 

40 

60 

80 

100 

120 

140 

180 

220 

.1 

0.0649 

0.151 

0.238 

0.324 

0.410 

0.497 

0.584 

0.670 

0.843 

1.020 

.2 

0.0644 

0.150 

0.236 

0.322 

0.408 

0.494 

0.579 

0.665 

0.837 

1.010 

.3 

0.0635 

0.148 

0.233 

0.317 

0.402 

0.487 

0.572 

0.656 

0.825 

0.995 

.4 

0.0624 

0.145 

0.229 

0.312 

0.395 

0.478 

0.561 

0.644 

0.810 

0.977 

.5 

0.0609 

0.142 

0.224 

0.304 

0.386 

0.467 

0.548 

0.629 

0.792 

0.955 

1.6 

0.0597 

0.139 

0.219 

0.299 

0.378 

0.458 

0.537 

0.617 

0.776 

0.935 

1-8 

0.0567 

0.132 

0.208 

0.283 

0.359 

0.435 

0.510 

0.585 

0.737 

0.888 

2.0 

0.0545 

0.127 

0.200 

0.279 

0.345 

0.418 

0.491 

0.563 

0.725 

0.854 

2  5 

0.0490 

0.114 

0.180 

0.245 

0.311 

0.376 

0.441 

0.507 

0.638 

0.768 

3.0 

0  0444 

0.103 

0.163 

0.222 

0.281 

0.340 

0.400 

0.459 

0.577 

0.696 

4.0 

0.0372 

0.0868 

0.136 

0.186 

0.235 

0.285 

0.335 

0.384 

0.483 

0.583 

5.0 

0.0324 

0.0756 

0.119 

0.162 

0.205 

0.248 

0.292 

0.335 

0.421 

0.508 

6.0 

0.0286 

0.0667 

0.105 

0.143 

0.181 

0.219 

0.257 

0.295 

0.371 

0.448 

7.0 

0.0257 

0.0599 

0.0942 

0.131 

0.163 

0.201 

0.231 

0.265 

0.334 

0.402 

8.0 

0.0233 

0.0545 

0.0856 

0.117 

0.148 

0.179 

0.210 

0.241 

0.303 

0.366 

9.0 

0.0215 

0.0501 

0.0788 

0.107 

0.137 

0.165 

0.193 

0.222 

0.279 

0.337 

10.0 

0.0199 

0.0463 

0.0728 

C.0994 

0.126 

0.152 

0.179 

0.205 

0.258 

0.311 

11.0 

0.0185 

0.0441 

0.0678 

0.0924 

0.117 

0.142 

0.166 

0.191 

0.240 

0.290 

12.0 

0.0173 

0.0403 

0.0633 

0.0864 

0.109 

0.132 

0.155 

0.183 

0.224 

0.271 

13.0 

0.0162 

0.0379 

0.0595 

0.0811 

0.103 

0.127 

0.146 

0.168 

Q.21'2 

0.254 

14.0 

0.0154 

0.0359 

0.0563 

0.0768 

0.0973 

0.118 

0.138 

0.159 

0.200 

0.241 

16.0 

0.0138 

0.0323 

0.0507 

0.0692 

0.0877 

0  106 

0.125 

0.143 

0.180 

0.217 

20  0 

0.0116 

0.0271 

0.0426 

0.0580 

0  0735 

0.089 

0.104 

0.120 

0.151 

0.182 

25.0 

0.0097 

0.0227 

0.0356 

0.0486 

0.0615 

0.0745 

0.0874 

0.101 

0.126 

0.152 

30.0 

0  0084 

0.0195 

0.0307 

0.0418 

0.0530 

0.0638 

0.0753 

0.0865 

0.109 

0.131 

NUMBER  OF  INDICATED    HORSE-POWER  FOR  EACH  CUBIC  FOOT  SWEPT  BY 
PISTON  PER  MINUTE  FOR  CONDENSING  ENGINES. 


INITIAL  PBESSUBE  IN  POUNDS  PEB  SQUABE  INCH  ABOVE  ATMOSPHEBE. 


No.  of 

Expan- 
sions. 

0 

20     40 

60 

80 

100 

120 

140 

180 

220 

1.1 

.0475 

0.184   0.221 

0.307 

0.393 

0  480 

0.567 

0.653 

0.826 

1.003 

.2 

.0470 

.133    .219 

.305 

.391 

.477 

.562 

.648 

.820 

0.993 

.3 

.0461 

.131    .216 

.300 

.385 

.470 

.555 

.639 

.808 

.978 

.4 

.0450 

.128    .212 

.295 

.378 

.461 

.544 

.627 

.793 

.960 

.5 

.0435 

.125  ]   .207 

.287 

.369 

.450 

.531 

.612 

.775 

.938 

.6 

.0423 

.122  i   .202 

.282 

.361 

.441 

.520 

.600 

.759 

.918 

.8 

.0393 

.115  |   .191 

.266 

.342 

.418 

.493 

.568 

.720 

.861 

2.0 

.0371 

.110    .183 

.262 

.328 

.411 

.474 

.546 

.708 

.837 

2.5 

.0316 

.097  I   .163 

.228 

.294 

.359 

.424 

.490 

,621 

.751 

3.0 

.0270 

.086    .146 

.205 

.264 

.323 

.383 

.442 

.560 

.679 

4.0 

.0198 

.0694   .119 

.169 

.218 

.268 

.318 

.367 

.466 

.566 

5.0 

.0150 

.0582   .102 

.145 

.188 

.231 

.275 

.318 

.404 

.491 

6.0 

.0112 

.0493   .088 

.126 

.164 

.212 

.240 

.278 

.354 

.431 

7.0 

.0083 

.0425   .0768 

.114 

.146 

.184 

.214 

.248 

.317 

.3fc5 

8.0 

.0059 

.0371    .0682 

.100 

.131 

.162 

.193 

.224 

.286 

.349 

9.0 

.0041 

.0327;   .0614 

.090 

.120 

.148 

.176 

.205 

.262 

.320 

10.0 

.0025 

.0289   .0554 

.0820 

.109 

.135 

.162 

.188 

.241 

.294 

11.0 

.0011 

.0264    .0504 

.0747 

.100 

.125 

.149 

.124 

.223 

.273 

12.0 

.0229    .0459 

.0690 

.092 

.115 

.138 

.166 

.207 

.254 

13.0 

.0205    .0421 

.0637 

.086 

.110 

.129 

.151 

.195 

.237 

14.0 

.  0185   .  0389 

.0594 

.0799 

.101 

!l21 

.142 

'l83 

.224 

16.0 

.  0149    .  0323 

.0518 

.0703 

.089 

.108 

.126 

163 

.200 

20.0 

.0097    .0252 

.0406 

.0561 

.0716 

.087 

.103 

.134 

.165 

25.0 



.0053   !oi82 

.0312 

.0441 

.0571 

.0700 

.084 

109 

.135 

30.0 

::::."" 

.0021    .0133 

.0244 

.0356 

.0464 

!o579 

.0691 

092 

.114 

STEAM  USING;  07?,  STEAM  ENGINE  PRACTICE. 


NUMBER  OF  INDICATED  HORSE -POWER  FOR  EACH  CUBIC  FOOT  SWEPT  BY 
PISTON  PER  MINUTE  IN  NON-CONDENSING  ENGINES. 


INITIAL  PBESSUBE    IN  POUNDS  PER  SQUARE  INCH  ABOVE  ATMOSPHERE. 


No.  of 

Expan 
sions. 

0 

20 

40 

60 

80 

100 

120 

140 

160 

220 

1 

0  073 

0  160 

0  246 

0.332 

0  419 

0.506 

0  592 

0  765 

0  942 

2 

0.072 

0.158 

0.244 

0  330 

0.416 

0  501 

0.587 

0  759 

0  932 

.3 

0.070 

0.155 

0.239 

0  324 

0.409 

0  494 

0.578 

0.747 

0.917 

.4 

0.067 

0.151 

0.234 

0.317 

0.400 

0.483 

0.566 

0.732 

0.899 

.5 

0.064 

0  146 

0  226 

0  308 

0.389 

0.470 

0  551 

0.714 

0.877 

.6 

8 

0.061 
0  054 

0.141 
0.130 

0.221 
0.205 

0.300 
0  281 

0.380 
0  357 

0.459 
0.432 

0.539 
0  507 

0.698 
0.659 

0.857 
0  810 

2  0 

0.049 

0.122 

0.201 

0.267 

0.340 

0.413 

0.485 

0.647 

0.776 

2.5 

0.036 

0.102 

0.167 

0.233 

0.298 

0.363 

0.439 

0.560 

0.690 

3  0 

0.025 

0  085 

0.144 

0  203 

0.262 

0  322 

0  381 

0.499 

0  618 

4.0 

0.009 

0.058 

0.108 

0.157 

0.207 

0.257 

0.306 

0.405 

0.505 

5  0 

0.041 

0.084 

0.127 

0  170 

0  214 

0  257 

0.343 

0  430 

6  0 

0.027 

0.065 

0.103 

0.141 

0.179 

0.217 

0.293 

0.370 

7  0 

0.016 

0.053 

0.085 

0.123 

0.153 

0.187 

0.256 

0.324 

8  0 

0  009 

0.039 

0.070 

0  101 

0  132 

0.163 

0.225 

0.288 

9  0 

0.029 

0.059 

0.087 

0.115 

0.144 

0.201 

0.259 

10  0 

0  021 

0.048 

0.074 

0.101 

0.127 

0  180 

0.233 

11.0 

0  014 

0.039 

0.064 

0.088 

0.113 

0.162 

0.212 

12  0 

0  009 

0  031 

0.054 

0.077 

0  105 

0  146 

0  193 

13  0 

0  025 

0.049 

0  068 

0  090 

0.134 

0  176 

14.0 

0  019 

0.040 

0.060 

0.081 

0.122 

0.163 

16  0 

0  010 

0  028 

0.047 

0.065 

0.102 

0  139 

20  0 

0.011 

0  086 

0.073 

0.104 

25.0 

0.009 

0.048 

0.074 

30.0 

0  031 

0.053 

CHAPTER      IV. 

ON  THE   INDICATOR,  THE   INDICATOR  DIAGRAM,  AND   THE  DIFFERENT 
CLASSES   OF   ENGINES. 

James  Watt  constructed  an  instrument  for  observing  the  volume  and 
pressure  of  the  steam  in  the  engine  cylinder  to  which  he  gave  the  name 
of  "Indicator."  It  consisted  of  two  parts:  One,  a  rectangular  frame  moving 
in  guides  backward  and  forward  and  actuated  by  the  engine,  to  the  beam 
of  which  it  was  connected  by  a  cord,  with  a  weight  or  spring  attached 
to  keep  the  cord  stretched.  In  this  way  the  frame  moved  with  the  piston, 
stopping  when  that  member  stopped,  and  corresponding  with  it  com- 
pletely. The  other  part  carried  a  small  cylinder  with  piston,  piston  rod, 
and  a  spring  in  connection  therewith.  Steam  being  admitted  to  this  cyl- 
inder from  the  engine  cylinder,  the  pressure  would  vary  and  the  piston 
would  consequently  rise  and  fall  within  the  cylinder  against  the  spring. 

By  attaching  a  pencil  to  the  top  of  the  piston  rod.  and  with  a  piece 
of  paper  secured  to  the  frame,  a  diagram  is  obtained  in  which  the  position 
of  a  point,  vertically,  in  relation  to  a  line  traced  when  the  steam  is  shut  off 
from  the  instrument,  is  governed  by  the  steam  pressure;  while  its  position 
horizontally  is  proportioned  to  the  movement  of  the  piston  of  the  engine, 
or  the  volume  occupied  by  the  steam.  The  diagram  thus  produced  is  pro- 
portioned to  the  pressure  in  height  and  to  the  volume  occupied  in  length, 
and  the  area  is  therefore  proportional  to  the  work  done  in  the  engine 
cylinder  per  stroke.  The  mean  pressure  in  pounds  per  square  inch  is 
found,  either,  by  measuring  at  ten  equi-distant  places,  or  by  measuring 
the  area  of  the  figure  and  dividing  by  the  length,  of  course  taking  into 
account  the  stiffness,  or  scale,  of  the  spring.  The  mean  pressure  times  the 
piston  area  in  square  inches  multiplied  by  the  stroke  in  feet  gives  the 
number  of  foot  pounds  per  stroke  of  engine. 

By  using  the  piston  speed  in  feet  per  minute,  in  place  of  the  stroke, 
and  dividing  this  by  33,000,  the  number  of  horse-power  exerted  is  deter- 
mined. 

By  using  a  mean  pressure  of  two  pounds  less,  the  number  of  net 
horse-power  may  be  estimated.  By  setting  off  the  line  of  no  pressure, 
14.7  pounds  below  the  atmospheric  line,  and  drawing  verticals  to  the  ends 
of  the  diagram,  and  by  using  this  as  the  diagram  of  an  engine  without  back 
pressure,  we  can  find  the  mean  total  pressure  and  the  number  of  total 
horse-power. 

In  such  an  instrument,  however,  there  are  many  imperfections.  The 
moving  springs  are  subjected  to  sudden  changes  of  pressure,  or  tension, 
and  vibrations  in  the  springs  are  set  up  by  the  inertia  of  the  moving  parts. 
This  is  true  for  both  the  pencil  and  paper  movements.  The  motion  of  the 


88 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


paper  from  the  engine  motion  is  subject  to  errors  both  geometric  and 
mechanical:  the  former  can  only  be  reduced  at  the  expense  of  the  latter. 

The  remedy  for  vibrations  of  spring  is  to  reduce  the  weight  of  the 
moving  parts,  to  decrease  the  amount  of  motion  therein,  and  to  increase 
the  stiffness  of  the  spring  itself. 

The  mechanical  errors  of  connection  are:  the  variations  in  length  of 
cords,  and  vibrations,  and  the  slack  in  the  bars  used  for  reducing  the  mo- 
tions. There  is  also  a  loss  in  pressure  caused  by  the  leakage  of  the  indi- 
cator piston,  and  for  engines  with  small  cylinders  an  error  is  introduced 
by  cylinder  condensation  in  the  indicator. 

In  large,  slow  moving  engines  these  errors  are  all  small  and  may  be 
neglected,  but  they  increase  in  importance  with  the  number  of  revolu- 
tions, and,  inversely,  with  the  size  of  the  engine. 

The  indicator  was  first  improved  by  McNaught,  with  Kichards,  Thomp- 
son, Crosby,  Tabor  and  Professor  Sweet,  following,  in  their  efforts  to  re- 
duce the  weight  of  the  moving  parts,  all  using,  however,  a  separate  in- 
strument. We  give  an  illustration  of  Thompson's  Indicator  as  a  good 
example. 


THOMPSON'S    STEAM     ENGINE    INDICATOR. 


OUTSIDE  VIEW. 


INSIDE  VIEW. 


ON  THE  INDICATOR,  ETC.  89 

M.  G.  A.  Hirn  employed  the  beam  of  the  engine,  the  deflection  being 
properly  multiplied,  for  the  spring  opposing  the  steam  pressure;  and  Mr. 
William  E.  Worthen  has  proposed  the  use  of  the  spring  of  the  cylinder 
head  of  the  engine  for  the  same  purpose.  This  would  give  very  satisfac- 
tory results  with  proper  means  for  multiplying  the  motion. 

In  France  a  device  has  been  tried  which  can  be  applied  to  engines 
running  with  nearly  constant  load,  but  which  is  not  well  suited  for  en- 
gines with  quick  acting  automatic  cut-off  gear.  An  adjustable  yoke  con- 
fines the  movement  of  the  pencil  within  narrow  limits,  and  by  changing 
this  adjustment  the  card  may  be  taken  piecemeal.  An  elegant  adaptation 
of  this  method  was  used  on  the  South  Eastern  Railway  of  France,  where 
the  adjustment  was  made  by  compressed  air,  and  the  diagrams  from  the 
cylinders  taken  in  the  dynamometer  car. 

Engines  may  be  classified  as  single  acting  and  double  acting,  accord- 
ing as  the  working  steam  is  used  in  one  or  both  ends  of  the  cylinder;  and 
condensing  and  non- condensing,  according  as  the  steam  from  the  cylinder 
is  cooled  by  water  and  condensed,  or  is  exhausted  directly  into  the  air. 

There  are  two  kinds  of  single-acting  engines.  The  one,  the  older,  is 
mainly  employed  in  the  pumping  of  water;  and  the  other,  the  modern  type, 
maintains  a  high  speed  of  revolution  on  a  shaft,  with  the  connecting  rods 
kept  under  stress  of  one  kind,  usually  compression,  so  that  the  shock  on 
the  boxes,  due  to  change  of  force  from  compression  to  tension,  and  the 
effects  of  wear,  are  avoided.  These  two  kinds  of  engines  are  entirely 
different  in  design  and  construction. 

The  oldest  form  of  engine  was  worked  by  admitting  steam  from  a 
boiler  to  the  cylinder,  below  the  piston,  which  was  connected  with  a  beam 
and  pump  rod.  The  weight  of  the  pump  rod  forced  the  water  up  from 
the  pump  and  also  carried  the  piston  to  the  top  of  the  cylinder.  A  jet 
of  water  was  then  thrown  into  the  cylinder  condensing  the  therein 
contained  steam,  which  had  been  previously  shut  off  from  the  boiler. 
The  pressure  of  the  atmosphere  now  drove  the  piston  down,  at  the 
same  time  lifting  the  pump  rod,  when  after  it  had  reached  the  bottom 
the  water  was  discharged  from  the  cylinder  and  the  process  was  re- 
peated. 

James  Watt  devised  the  separate  condenser  and  covered  the  cylinder 
so  as  to  introduce  steam  at  its  upper  end,  thereby  lifting  the  pump  rod. 
When  the  piston  reached  the  bottom  of  the  cylinder  the  steam  was  cut  off 
from  the  boiler.  An  arrangement,  called  the  equilibrium  valve,  opens 
communication  between  the  two  ends  of  the  cylinder,  and  the  steam 
now  pressing  equally  above  and  below  the  piston,  the  weight  of  the 
pump  rod  carries  the  piston  to  the  top  of  the  cylinder,  driving  the  steam 
which  was  above  the  piston  to  its  lower  end,  and  doing  the  pumping  at 
the  same  time.  The  steam  is  now  admitted  above  the  piston  as  before, 
but  the  bottom  of  the  cylinder  is  opened  to  the  condenser  and  a  vacuum 
is  produced  below  the  piston  at  the  same  time  as  the  steam  exerts  its 
pressure  above  it. 

These  engines  were  introduced  into  the  mines  of  Cornwall,  and  into 


90  STEAM  USING;  OR,  STEAM  ENGINE  PE ACTIVE. 

deep  shafts,  and  with  ample  boilers  and  high  pressure  steam  they  became 
famous  as  the  "Cornish  Pumping  Engines."  With  the  quick  admission 
of  high  pressure  steam  a  sudden  pull  was  exerted  on  the  pump  rods, 
which,  being  constructed  of  wood  and  of  long  length,  readily  absorbed 
this  jerk  and  began  to  rise.  An  early  cut-off  allowed  the  rapidly  falling 
steam  pressure  in  the  cylinder  to  be  helped  out  by  the  inertia  of  the 
weight  lifted,  which  came  slowly  to  rest,  and  then  reacted  upon  the 
column  of  water,  commencing  gradually, — conditions  very  favorable  for 
the  pumping  part  of  the  work.  The  boilers  used  gave  very  high  evapora- 
tion by  reason  of  the  very  moderate  manner  in  which  they  were  worked, 
and  the  duty,  or  number  of  foot  pounds  of  water  raised  per  pound,  or  per 
bushel  of  coal,  was  also,  usually  very  high.  In  these  mines  systematic 
record  was  kept  and  published  monthly,  and  competition  was  thus 
induced  among  the  men  in  charge  of  the  engines.  High  pressure  steam 
and  high  expansion  here  received  its  first  practical  confirmation. 

When,  however,  these  engines  were  applied  to  pumping  water  for 
water  works,  it  was  found  that  without  the  elasticity  of  the  long  and 
heavy  pump  rods  used  in  the  mines,  the  pump  was  apt  to  jump,  if  high 
pressure  steam  was  used;  that  is,  the  plunger  would  rise  without  the  pump 
filling  and  a  very  hard  shock  was  the  result.  In  consequence  the  use  of 
high  pressure  steam,  and  high  expansion,  was  abandoned  in  such  engines 
built  for  waterworks  purposes  in  the  United  States,  and  it  is  safe  to  say 
that  for  such  purposes  no  more  of  this  class  of  engine  will  ever  be  built  in 
this  country.  In  no  case  where  used  for  water  works  has  any  such  duty 
been  reached  as  was  obtained  by  these  engines  in  the  mines.  The  indicator 
diagrams  for  this  class  of  engines  are  to  be  placed  one  above  the  other;  any 
difference  between  the  exhaust  line  of  the  steam  end  and  the  admission 
line  of  the  exhaust  end  being  so  much  lost  pressure  and  work. 

In  the  class  of  Cornish  engines,  introduced  by  Captain  Bull,  the  beam 
was  dispensed  with  and  the  cylinder  placed  directly  over  the  pump,  the 
steam  being  introduced  at  the  lower  and  the  exhaust  taken  from  the 
upper  end.  A  pair  of  such  engines  are  used  at  the  Kiver  Pumping  Station 
of  the  St.  Louis  Water  Works,  but,  as  suggested  above,  with  steam  at  a 
low  pressure.  The  diagrams  given  herewith  show  the  limited  expansion 
possible. 

The  other  class  of  single  acting  engines  was  introduced  in  order  to  at- 
tain a  higher  speed  of  rotation  than  had  been  found  convenient  in  the  or- 
dinary double  acting  engines,  where  the  inertia  of  the  rods  and  the  change 
from  thrust  to  tension  brings  first  one  side  of  the  box  and  then  the  other 
into  bearing.  Unless  this  change  is  a  gradual  one  it  is  accompanied  by  a 
shock  more  or  less  disastrous  to  the  machine.  By  keeping,  say,  a  thrust 
continually  on  the  rods  the  boxes  are  always  in  bearing  on  one  side  and  no 
such  shock  occurs.  The  steam  during  admission  and  expansion  causes 
a  pressure  in  one  direction  on  the  piston  which  is  not  changed  during 
exhaust  and  compression.  The  irregularity  of  action  may  be  remedied  by 
a  heavy  fly-wheel  or  by  the  use  of  one  or  more  cylinders.  As  examples: 
for  two  cylinders  engines  we  select  the  Westinghouse;  for  engines  with 


OJV  THE  INDICATOR,  ETC. 


91 


three  cylinders,  Brotherhood's,  of  London;  and  with  six  cylinders,  the 
Colt  Disc  Engine,  from  West's  and  Darkin's  patents,  manufactured  by  the 
Colt's  Fire  Arms  Company,  of  Hartford,  Conn.  These  machines  have,  at 
the  time  of  writing,  been  used  more  particularly  with  electric  apparatus, 
and  in  small  boats,  but  have  attained  much  popularity  in  other  directions. 
The  exhaust  is  taken  into  the  chamber  where  it  lubricates  the  main 


DIAGRAM  FROM  CORNISH  ENGINE,  No.  1,  Low  SERVICE, 
ST.  Louis,  Mo.,  WATER  WORKS. 

56"  X  138"  X  9  double  strokes  per  minute. 


30-i 


20- 


10- 


DIAGRAM  FROM  ENGINE  No.  1,  HIGH  SERVICE,  ST.  Louis,  Mo., 
WATER  WORKS. 

85"  X  120"  X  11%  revolutions  per  minute.    I.  H.  P.  705. 


92  •  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


THE    WESTINGHOUSE    ENGINE. 


FRONT  VIEW.    160  H.  P. 


VARIETIES  OF  ENGINES. 


THE    WESTINGHOUSE    ENGINE. 


REAR  VIEW.    160  H.  P.    (One  fly-wheel  removed.) 


94 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


THE    WESTINGHOUSE    ENGINE. 
SECTION  THROUGH  SHAFT. 


9 


A  A,  Cylinders.  B,  Valve  Chamber.  6',  Bed,  or  Crank  Case.  1)  1),  Pistons.  F  F, 
Connecting  Rods.  G  G,  Cranks.  H  H,  Crank  Shaft.  /,  Eccentric.  ,7,  Valve  Guide. 
K,  Centre  Bearing.  M,  Steam  Connection.  N,  Exhaust  Connection.  7?,  Oil  Pipe.  V, 
Valve.  W,  Wiper.  Y,  Fly-Wheel.  Z,  Pulley,  a  a,  Cylinder  Heads,  b  b,  Steel  Wrist 
Pin.  c,  Crank  Case  Head,  d  d,  Crank  Shaft  bearings,  d'  Cover,  e,  Oil  Passage.  //,  Oil 
Cups.  Q  g,  Bolts,  h,  Bonnet,  j  j,  Spider  Heads,  k  k,  Rings.  I,  Hollow  Valve  Bolt. 
»,  Syphon  Overflow,  o,  Hole  in  Funnel  Head,  r,  Eccentric  Rod.  1 1,  Collar  Washers. 
?',  Lead  Washer,  x  x.  Bobs  on  Crank. 


96 


STEAM  USING-:  OR,  STEAM  ENGINE  PRACTICE. 


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97 


STEAM  USING;  OR,  STEAM  EN&IXE  PRACTICE. 


THE    BROTHERHOOD    THREE-CYLINDER    ENGINE. 


PERSPECTIVE  ELEVATION. 

bearing  with  the  wet  steam  and  the  oil  introduced  by  the  steam  pipe.  The 
Brotherhood  engines  are  also  used  with  compressed  air  for  driving  tor- 
pedoes, and  we  have  seen  one,  driven  by  a  Westinghouse  Air  Compressor 
used  for  drilling  in  a  locomotive  repair  shop. 

It  appears  to  us  that  these  engines  are  well  adapted  for  constant  work, 
but  for  intermittent  use  the  temptation  to  run  them  without  cleaning  must 
be  so  great  as  to  render  them  liable  to  a  rapid  deterioration. 

When  indicator  diagrams  from  large,  slow  moving  engines  are  exam- 
ined, and  the  weight  of  steam  present  at  any  two  points  of  the  stroke,  such 
as  at  cut-off,  and  release,  is  calculated  by  the  aid  of  the  table  of  the  "Pro- 
perties of  Steam,"  and  the  volume,  pressure,  and  density  thereof,  we  shall 
rarely  find  any  kind  of  agreement  in  the  two  results.  And,  if  there  has 
been  also  a  careful  measurement  of  the  quantity  of  feed  water  consumed 
per  stroke,  the  amount  will  be  found  to  be  much  in  excess  of  that  given  by 


VARIETIX8  OF 


99 


THE    COLT    DISC    ENGINE. 
West's  and  Parkin's  Patents. 


PERSPECTIVE  ELEVATION. 


computation.  This  difference,  in  an  engine  with  a  tight  piston,  is  only  to 
be  accounted  for  by  the  action  of  the  metal  of  the  cylinder  which  transfers 
heat  to  and  from  the  within  contained  steam.  This  has  already  been  ex- 
plained in  Chapter  III.  We  shall  consider  the  effect  of  this  action  upon 
the  indicator  diagram,  and  the  loss  of  work  which  occurs  compared  with 
that  which  should  be  done  in  a  non-conducting  cylinder;  or,  in  other 
words,  the  consequent  increase  in  the  quantity  of  steam  used  for  a  given 
work  shown. 

Let  us  take  for  example  the  data  of  the  experiment  conducted  by  Mr. 
J.  W.  Hill  at  the  Miller's  Exhibition,  held  at  Cincinnati.  The  experiment 
from  which  we  obtain  the  following  was  made  upon  one  of  three  Corliss 
engines,  built  by  different  makers,  but  all  having  the  same  general  dimen- 
sions, viz: 


100  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


THE    COLT    DISC    ENGINE. 


LONGITUDINAL    SECTION. 


CROSS  SECTION,   SHOWING   CIRCULAR  VALVE,  PORTS,   ETC. 


VAltTETIE*  OF  EX'r/XES. 
THE    COLT    DISC    ENGINE. 


101 


CROSS  SECTION,   SHOWING  INTERIOR  OF  ENGINE,    STEAM  PORTS  AND 
EXHAUST    PASSAGES 

The  main  body  of  the  engine  consists  of  one  casting,  containing  six  cylinders, 
arranged  in  a  circle,  and  parallel  with  one  another.  The  pistons  A  take  the  form  of  a 
hollow  plunger,  one  end  terminating  in  a  blunt  cone  which  bears  continuously  against 
the  periphery  of  the  disc  B.  They  are  single  acting,  being  subject  to  steam  pressure 
upon  the  flat  end  only.  Steam  is  admitted  successively  to  the  six  cylinders  from  the 
steam  chest  C,  three  pistons  being  constantly  in  action  at  different  points  of  the  stroke, 
thereby  imparting  a  uniform  rolling  motion  to  the  conical  disc  B,  which  is  steadied  at 
its  center  by  the  ball  and  socket  joint  D,  and  rolls  upon  the  conical  surface  of  the  back 
plate  £,  which  receives  the  full  thrust  of  the  pistons,  and  protects  the  ball  and  socket 
joint  1)  from  strain.  The  crank  pin  F  is  securely  fixed  in  the  centre  of  the  conical  disc 
/»,  the  rolling  motion  of  the  disc  causing  the  pin  to  describe  a  circle,  and  by  means  of 
the  crank  G,  imparting  a  rotary  motion  to  the  shaft  H.  The  shaft  Jf  passes  through  the 
centre  of  the  steam  chest  and  carries  an  eccentric  giving  motion  to  the  circular  valve  K. 
The  valve  K  is  a  flat  circular  ring  which  slides  steam  tight  but  perfectly  freely  between 
the  port  face  and  a  balance  plate.  The  steam  is  admitted  to  and  fills  the  annular  space 
f '  left  in  the  steam  chest  outside  the  circumference  of  the  valve  ring  K,  the  eccentric 
motion  of  which  alternately  opens  and  closes  all  the  steam  ports,  successively  admitting 
steam  to  the  cylinders,  from  which  it  again  escapes  to  the  exhaust  chamber  M  formed 
by  the  inside  of  the  valve  ring,  and  thence  through  openings  into  the  body  of  the  engine, 
and  is  finally  discharged  by  the  exhaust  pipe  3", 


102 


STEAM  VSIXG;   OJt,  STEAM  ENGINE  PRACTICE. 


ON  THE  INDICA  TOE,  ETC.  1O3 


Cylinder,  18"  x  48";  number  of  revolutions,  75.4;  steam  at  80  pounds 
pressure,  cutting  off  at  13  per  cent,  of  the  stroke  for  the  Allis  Engine:  cut- 
off pressure,  84  pounds;  piston  area  =  1.7  square  feet;  piston  displace- 
ment =  6.8  cubic  feet; 

13  per  cent,  of  6.8  =  0.884  cubic  feet. 

Clearance  volume  =  0.2  cubic  feet;  volume  occupied  by  steam  at  cut-off, 
1.084  cubic  feet;  density  of  steam  at  84  pounds  =  0.231; 

0.231  x  1.084  =  weight  of  steam  at  cut-off  =  0.250  pounds; 
weight  of  feed  water  per  hour  =  3422.6  pounds;  weight  of  feed  water  per 
stroke  =  0.378  pounds: 

0.378  —  0.250  =  0.128  pounds  condensed  at  cut-off; 

or,  34  per  cent,  of  all  the  fluid  present  is  water;  or,  the  water  present 
equals  in  weight  50  per  cent,  of  the  steam. 

Real  expansion  =  -~-  =  6.4. 

Now  taking  the  length  of  the  diagram  to  represent  6.8  cubic  feet,  and 
adding  the  clearance  =  0.2  cubic  feet,  or,  say  3  per  cent,  of  the  stroke,  we 
set  off  at  the  cut-off  pressure  a  volume  50  per  cent,  greater  than  the  cut-off 

loor 


DlAGEAM  FROM  REYNOLD'S   CORLISS  ENGINE, 
Cylinders  18"  X  48"  X  75  revolutions  per  minute,  at  Millers'  Exhibition,  Cincinnati,  O. 

volume;  and  if  from  this  point  we  draw  a  curve  of  expansion  for  steam  in  a 
non-conducting  cylinder  till  we  reach  the  pressure  of  release,  and  thence 
draw  a  vertical  line  to  the  back  pressure,  we  have  the  diagram  which  the 
water  boiled  should  have  given  per  stroke  in  a  non-conducting  cylinder; 
and  the  difference  between  the  area  of  this  diagram  and  the  real  diagram 
represents  the  loss  which  has  taken  place  by  the  action  of  the  sides  of  the 
cylinder.  Measuring  the  area  of  the  diagram  by  the  planimeter  we  have 
4.40  square  inches,  and  for  the  area  of  the  new  diagram,  5.91  square  inches, 
which  makes  the  latter  0.34  per  cent,  larger.  The  indicated  horse-power 


104  STEAM  USING;  Oil,  STEAM  ENGINE  PRACTICE. 


is  152.7,  which  in  a  non-conducting  cylinder  would  be  nearly  204,  so  that 
a  loss  of  50  indicated  horse-power,  or,  say  25  per  cent.,  is  caused  by  the 
transfer  of  heat  in  the  sides  of  the  cylinder. 

This  experiment  is  a  good  one  by  which  to  examine  other  matters,  so 
that  we  may  see  what  can  be  obtained  from  an  indicator  card. 

In  the  above  experiment  the  quantity  and  rise  of  temperature  of  the 
injection  water  were  measured,  and  the  steam  supplied  was  found  to  be 
dry  by  calorimeter  tests.  We  abstract  from  the  report  of  the  trial  the 
following: 

Dry  steam  supplied  per  hour  for  ten  hours  ..........  3422.6       pounds. 

Dry  steam  per  stroke  ..................................  0.3782  pounds. 

The  injection  water  =  30.88  times  the  feed  and  rose  from  72°  to  102° 
Fahr.,  which  gives  0.3782  x  30.88  x  30  =  351  heat  units  rejected  per  stroke. 
Mean  indicated  pressure  ......................  34.26  pounds. 

Mean  total  pressure  ...........................  40.5    pounds. 

Area  of  piston  ................................  253       square  inches. 


Total  work  per  stroke  =         —       _    4  =  53  units. 

Heat  per  stroke,  feed  at  32°  =  0.3782  x  1181  ..................  446  units. 

Deduct  for  feed  at  102  —  32  =  0.3782  x      70  ..................  26      " 

Heat  given  to  engine  per  stroke  ............................  420     " 

Heat  expended  in  work  per  stroke  ............  .  ..........  53 

Heat  in  external  radiation,  say  ..........................     4      57 

363      " 
Heat  found  in  rise  in  injection  water  .......................  351 


12 


12 
Error  in  measurement  =  — — ,  or,  say  3  per  cent. 


This  error  in  the  experiment  probably  arose  in  the  measurement  of  the 
injection  water,  and  perhaps,  from  not  obtaining  the  average  of  the  hot 
well  accurately. 

At  cut-off  we  observed  that  of  the  amount  of  0.378  pound  of  feed 
water  evaporated  per  stroke,  0.25  pound  was  steam,  while  the  balance, 
equal  to  0.1282  pound,  had  condensed. 

Units. 

At  this  time  the  internal  heat  of  the  steam  present  = 1100  x  0.25  =  275 

water        "         =...298X0.1282=    38 
275  —  38  =  313,  or, 

Heat  in  fluid  present 313 

Heat  received  from  boiler  as  given  above 446 

Heat  absorbed  by  cylinder  =  446  —  313  = 133 


OX  THE  INDICATOR,  ETC.  1O5 

At  the  end  of  the  stroke  the  volume  occupied  is  7  cubic  feet,  with  a 
total  pressure  of  12  pounds;  density  =  0.031: 

Weight  of  steam  present,  7  x  0.031 0.217    pounds. 

Weight  of  water  present,  0.3782  —  0.217 0.1612  pound. 

Internal  heat  in  steam  present,  0.217  x  1072 . . .233  units. 

Heat  in  water  present,  0.1612  x  170 27    " 

Heat  in  fluid  present 260    " 

Heat  used  in  expansion 36     " 

u 

Heat  accounted  for 296    " 

Heat  in  fluid  at  cut-off 313    " 

Heat  added  to  iron  during  expansion,  313  —  296 17    " 

Heat  in  iron  at  end  of  stroke,  133  4-17 150    " 

And  this  latter  amount  is  necessarily  thrown  away  during  the  exhaust, 
from  the  iron  of  the  cylinder  into  the  condenser,  and  is  the  cooling  effect 
of  the  latter  upon  the  former. 

The  computation  at  the  end  of  the  stroke  is  never  so  satisfactory  as  at 
cut-off,  because  the  changes  of  volume  are  much  greater  for  small 
changes  of  pressure  with  low  pressure  steam  than  with  high.  Suppose 
for  instance  the  terminal  pressure  be  taken  as  2  pounds  below  the  atmos- 
phere instead  of  3.  The  density  will  equal  0.034,  and  the  weight  of  steam 
0.238  pounds,  while  its  internal  heat  will  equal  0.238  x  1072  =  255  units. 

94- 

The  water  will  equal  0.1402  pounds  and  its  heat  =         . 

279 

This  will  make  19  units  more  accounted  for  in  the  fluid  present,  and 
will  give  131  units  in  the  iron  at  the  end  of  the  stroke,  instead  of  150,  by 
reason  of  the  cooling  effect  of  the  condenser.  If  the  agreement  between 
the  heat  rejected  and  that  given  from  the  boiler  had  been  closer,  we 
should  have  found  a  check  upon  this  cooling  effect  of  the  condenser,  as 
follows: 

Heat  found  in  condenser. 351  units. 

Heat  given  by  back  pressure  work 7 

Fluid  heat  at  end  of  stroke,  260  or  279  units,  according  to  the  terminal 
pressure  taken.  But  this  is  too  large,  as  the  temperature  of  the  water  in 
the  condenser  is  102°  and  not  32°,  and  we  have  0.3782  x  70  =  26  units  to  de- 
duct as  before,  which  leaves  234  or  253  units  received  into  the  condenser 
from  the  fluid;  or  from  the  fluid  and  work  of  exhaust  241  or  260  units. 
Deducting  these  amounts  from  351  units,  we  have  110  or  91  units  as  the  heat 
received  from  the  iron;  but  if  we  had  found  13  units  more  in  the  condenser 
the  values  would  be  123  and  104  units,  thus  rendering  the  lower  value  of 
terminal  pressure  the  more  probable.  A  very  slight  amount  of  water  in  the 
steam  supplied  would  account  for  much  of  the  inconsistency  of  these 
results.  We  shall  give  in  Chapter  V  examples  of  such  computations  by 
M.  O.  Hallauer,  showing  more  consistent  results. 

With  the  use  of  high  pressure  steam,  and  high  expansion,  as  employed 
by  Trevithick,  in  Cornwall,  the  shock  and  change  of  pressure  in  the  cyl- 


1O6 


STEAM  USING:   OE,  8TEAM  ENGINE  PRACTICE. 


inder  between  the  beginning  and  end  of  the  stroke,  of  course,  became 
considerable,  and  it  was  suggested  by  Hornblower,  in  England,  and  long 
afterwards  by  Woolf,  in  Germany,  that  the  steam  should  be  first  introduced 
into  a  small  cylinder,  whereby  the  strain,  produced  on  the  connections  by 
the  sudden  influx  of  high  pressure  steam,  might  be  reduced,  and  that  after 
acting  for  more  or  less  of  the  stroke  at  boiler  pressure,  the  steam  should 
be  put  in  communication  with  a  larger  cylinder  in  which  the  expansion 
should  be  completed.  But  while  pushing  the  large  piston  forward  there 
is  a  tendency  to  retard  the  motion  of  the  small  one.  The  following  dia- 
gram, Fig.  40,  will  explain  the  indicated  work  and  the  total  work: 


FIG.  40. 

Let  a  b  represent  the  volume  of  the  small  cylinder,  b  c  the  clearance 
between  the  small  and  large  cylinder  and  a  b  +  c  d  the  volume  of  the 
large  cylinder. 

The  area  a  g  f  e  b  is  the  total  work  done  in  the  small  cylinder  and  the 
area  a  n  i  h  j  k  d  is  the  total  work  done  in  the  large  cylinder.  The  indi- 
cated work  of  the  small  cylinder  is  n  g  f  e  and  the  back  pressure  work  is  a 
neb.  The  indicated  work  of  the  large  cylinder  is  n  i  h  j  k  n,  while  the 
back  pressure  work  is  a  n  k  d.  We  see  that  the  work  a  nm  b  has  been 


VARIETIES  OF  XX'rlXJ-s.  1O7 

counted  twice,  which  is  once  too  many;  and  we  also  see  that  there  are  two 
ways  of  representing  the  portion  n  m  i,  which  may  be  considered  as  part 
of  the  back  work  of  the  small  cylinder  while  it  is  forward  work  for  the 
large  cylinder.  Or  we  take  it  as  part  of  the  forward  work  of  the  small 
cylinder,  giving  a  g  fe  b  as  the  forward  work,  while  a  n  m  b  is  the  back 
pressure  work  in  that  cylinder,  leaving  n  gfe  m  as  the  indicated  work; 
while,  for  the  large  cylinder  we  have  chjd  for  the  total,  I  hj  k  for  the 
indicated  and  elk  d  for  the  back  pressure  work. 

If  the  receiver  between  the  cylinders  be  small,  the  pressure  at  the  be- 
ginning of  the  stroke  of  the  large  cylinder  is  nearly  equal  to  that  at  the 
end  of  the  stroke  of  the  small  cylinder.  With  a  large  receiver  the  press- 
ure is  apt  to  be  much  less,  while  it  can  be  raised  by  a  cut- off  on  the  large 
cylinder. 

The  amount  of  clearance  volume  between  the  cylinders  affects  the 
form  of  the  curves  e  n  hj  and  i  n;  and  when  very  large,  regarding  c  d,  the 
work  done  in  each  cylinder  is  measured  by  itself  without  any  deductions 
and  the  diagrams  are  placed  one  under  the  other,  as  in  figure  41,  where: 
a  b  c  d  e  a  is  the  high  pressure  diagram,  and  a  f  g  h  k  the  low  pressure  dia- 
gram. The  enclosed  areas  are  the  indicated  work;  the  area  j  k  hi  the 
back  pressure  work  on  the  large  piston,  and  a  e  m  j  that  of  the  small 
piston. 

When  the  question  of  indicated  power  only  is  under  discussion  the 
measurement  of  the  diagram  by  the  ordinates  or  by  the  planimeter  is  suf- 
ficient. Each  piston  by  itself  is  taken  and  the  work  done  on  it  found  and 
added.  Much  misconception  of  this  subject  appears  to  have  prevailed, 
and  one  modern  writer  claimed,  in  1883,  a  generalization  and  geomet- 
rical construction  which  is  given  in  Rankine's  Steam  Engine,  in  the  first 
edition. 

Many  forms  of  compound  engines  are  to  be  met  with,  some  of  which 
may  be  briefly  described  as  follows: 

1 .  Engine  with  two  cylinders  of  equal  stroke  acting  on  one  crank  pin, 
the  steam  from  one  end  of  the  small  cylinder  passing  to  the  farther  end 
of  the  large  one.     The  cylinders  are  usually  in  line,  or  "tandem." 

2.  Engine  with  two  unequal  cylinders  attached  to  the  same  end  of  a 
beam,  the  steam  passing  from  one  end  of  the  small  cylinder  to  the  further 
end  of  the  large  one.     This  form  was  the  original  one  introduced  by  Woolf . 

3.  Engine  with  two  cylinders  of  the  same  diameter,  set  side  by  side, 
with  two  cranks  at  180°,  the  steam  from  the  small  cylinder  passing  across 
to  the  near  end  of  the  large  one. 

4.  Engine  with  two  cylinders  attached  to  opposite  ends  of  a  beam,  the 
steam  from  the  top  of  the  small  cylinder  passing  to  the  top  of  the  large. 
This  form  has  been  largely  used  by  McNaught  and  lately  with  horizontal 
cylinders. 

5.  Engine  with  two  cylinders  attached  to  two  cranks  at  an  angle  of 
90°  with  each  other  and  a  more  or  less  intermediate  receiver.     With  verti- 
cal cylinders  they  have  been  more  used  than  any  other  form  for  marine 
engines. 


1O8  STEAM  rslXf,',-  (HI,  STEAM  ENGINE  PRACTICE. 


6.  Engines  with  three  cylinders  attached  to  cranks  at  120°  with  each 
other,  one  of  them  being  used  for  high  pressure  and  the  two  others,  of  the 
same,  or  greater  diameter,  for  low  pressure.     This  class  has  been  success- 
fully used  on  the  very  largest  marine  engines.     Those  of  the  steamships 
Arizona,  Alaska,  Servia,  Aurania  and  Oregon  may  be  instanced. 

7.  Engine  with  four  equal  cylinders  attached  to  cranks  at  45°,  using 
one  as  high  pressure  and  the  other  three  as  low  pressure. 

8.  Two  pairs  of  tandem  engines  driving  two  cranks  at  90°. 

9.  Three  pairs  of  tandem  engines  driving  three  cranks  at  120°. 

10.  Three  unequal  cylinders  driving  three  cranks  at  120°,  the  steam 
passing  through  all  three  cylinders. 

11.  Two  pairs  of  tandem  engines  driving  two  cranks  at  90°,  the  steam 
passing  through  all  four  cylinders  and  two  interheaters. 

The  use  of  receivers  of  comparatively  large  volume  between  two  cyl- 
inders was  first  suggested  by  Ernest  Woolf,  and  the  great  progress  made 
in  marine  engines  by  its  use,  under  the  name  of  compound  engines,  has 
been  mainly  due  to  its  adoption  by  the  engineers  of  Glasgow. 

For  marine  service  the  compound  engine  with  high  pressure  steam 
has  developed  the  best  practical  results.  The  most  usual  type  adopted  is 
that  with  two  cylinders,  the  smaller,  or  high  pressure,  and  the  larger  or 
low  pressure,  being  coupled  by  cranks  at  90°.  The  most  usual  type  of 
screw  engine  being  vertical,  we  find  the  small  cylinder  occasionally  placed 
on  top  of,  and  in  line  with,  the  large  cylinder,  both  pistons  working  on 
the  same  rod.  Two  or  three  such  engines  are  used  with  cranks  at  90°  with 
two  cylinders,  and  at  120°  when  three  cylinders  are  employed. 

When  the  use  of  two  cylinders  would  require  the  low  pressure  cylin- 
der to  be  excessively  large,  two  low  pressure  cylinders  are  used  in  connec- 
tion with  one  high  pressure  cylinder,  coupled  to  cranks,  generally  at  120°. 

The  use  of  three  cylinders  of  different  sizes  has  been  tried  with  steam  at 
125  and  140  pounds  pressure,  the  higher  pressure  was  adopted  on  the  Steamer 
Propontis.  Although  the  boilers  in  this  instance  had  to  be  abandoned,  the 
results  were  very  good  while  the  high  pressure  could  be  maintained. 

The  following  table  prepared  with  great  care  by  Mr.  Marshall  gives 
the  results  of  the  progress  in  marine  engine  practice.  While  the  economy 
in  the  use  of  high  pressure  steam  and  the  compound  engine,  taken  to- 
gether, is  evident,  it  must  be  confessed  that  it  is  not  easy  to  separate  the 
effects  of  the  two  causes;  and  while  the  mechanical  advantages  of  com- 
pounding for  marine  engines  of  large  size,  for  which  it  is  especially  useful, 
are  well  known,  yet  it  may  be  stated  that  with  steam  of  moderate  pressure 
no  advantage  in  economy  has  been  found  when  the  compound  engine  is 
compared  with  single  cylinder  engines  of  good  design  and  construction, 
and  working  steam  at  the  same  pressure. 

It  is  also  readily  conceded  that  higher  rates  of  expansion  may  be  used 
with  the  compound  engine  than  with  single  cylinder  engines,  using  steam 
at  the  same  pressure;  but  it  may  be  doubted  whether  any  practical  econ- 
omy has  resulted  therefrom,  as  may  be  seen  from  an  examination  of  the 
table  of  engine  trials  and  the  paper  by  Hallauer  in  Chapter  V. 


VARIETIES  UF 


109 


THE  AVERAGE  CONSUMPTION  OF  COAL  PEE  I.  H.  P.  PER  HOUR, 

By  Steamships  using  Compound  Engines  in  long  sea  voyages.  A  table  reduced  from 
one  accompanying  a  paper  read  before  the  Institution  of  Mechanical  Engineers,  Lon- 
don, in  1881,  by  F.  C.  Marshall. 


s 

I 

®      Cylinders. 

^    Receivers  at 

o             90°. 

6 

| 

Piston         g 
Speed.         g 

s 

o 

lifi  i 

cc             *<      4 

°      Ms   1 

s       -as    o 

.5            °<       0 

otal  Heating 
Surface. 

rate  Area. 

idicated  Horse- 
Power. 

oal  in  Pounds 
per  I.  H.  P.  per 
hour. 

X. 

a 

Si 

H 

-i  - 
a^ 

fe 

o 

0             £           2 

H           0 

i—  i          o 

H 

Ft.       sq.  ft. 

ft.  in. 

•         -. 

sq.  ft.  sq  ft. 

1  34&61X45 

450            2466 

15    3             70           5 

>     4216    140 

900                1.5 

14.00 

'1  4  '2  A:  SOX  48 

552 

72  5        ci 

>      6000  

1881                l.t? 

32  25 

3  36*70X48 

400            2400 

17     0              90            5 

!      4440    160 

1200                1.63 

2l'" 

4  46*87X57 

484            5000 

19     0              80            ' 

t      7803    25U 

2200                1.66 

40 

5  22*44X30 

360              705 

11     0            100            ] 

Lj     1402      49.5 

920               1.67 

7.5 

6  50*86X54 

540            4865 

17     6              72            4 

t      7722    273 

2673               1.67 

48 

7  35  &  70X48 

424            2000 

17     0              90            J 

5      4774    150 

1200                1.69 

21.5 

8  54*94X60 

530            7420 

18    3%          75            ( 

\    10839    313 

2207                1.70 

40.3 

9  54*94  X  60 

486           7422 

18     0              82.5        ( 

5    11340    324 

1801                1  70 

32.8 

in  Hn*5SX39 

400            1513 

14     2              80            ! 

!j     2608      69.7 

650                1.72 

12 

11  29&  56X33 

350            1250 

13     3              70            J 

2      2379      66 

500                1.76 

9.5 

12  34*66X42 

406            1700 

15     6              80            • 

>;     3474    107.2 

875                1.76 

16.5 

13  36*68X42 

434            1821 

16    3              77            i 

\-     3714    110 

854                1.76 

16.75 

14  54*97X60 

480            7427 

18  10%          70            ( 

5    11045    329 

2000                1.80 

38.6 

ir>  51*88X60 

590            5000 

17     6              75 

['•     9248    332.5 

2745                1.83 

54. 

16  28*53X38 

380            1560 

14     n              75            ! 

>      2433      78 

560                1.84 

11 

17  50&86X54 

540            5500 

17    6              70 

I      7525    273 

2422                1.85 

48 

18  38*70X48 

416            2600 

17     9              80 

4864      65 

1160                1.85 

23 

19  35&70X48 

408            2005 

17     0              90            5 

J      4826    150 

1099                1.87 

22 

2035*70X48 

440           2000 

20     9              90 

J      4396    136 

1135                1.89 

23 

21  341»&64X42 

560            1647 

15     4              80 

>      2950    106 

880                1.90 

18 

22  48&84X60 

550           4468 

19     0              70            I 

{      8200    340 

2300                1.90 

47 

23  50*86X54 

510            4842 

17     9              70            ( 

5      9839    310 

2213                1.90 

43.5 

24  54&94X60 

441            7420 

17     9              70         i 

*,    11750    312 

2400                1.90 

48.9 

25  56&97X54 

504            5000 

18     6              7d 

;      8215    292 

2500                1.93 

51.9 

26  30*60X36 

372            1600 

13     0              90 

J      2753    115 

600                1.94 

12.5 

27  36*70X45 

560            2900 

13     0              75 

I      4622    166 

1600                2.00 

32 

28  36*64X36 

450            2059 

13    0              70 

I      2854    106 

1020                2.12 

22 

29  36&68X42 

530            2500 

13     0              70 

>      3462    130 

1250                2.25 

29 

3036*67X42 

530            2400 

13     0              70         , 

I      3451    129 

1230                2.25 

28 

mean  467 

mean  77.4 

mean  1.828 

Tandem— 

31  48*83  X60d'ble. 

523            9000 

23     6              70 

3    19104    624 

4900               1.77 

93 

32  26*58X45  Sin. 

444            1700 

15    0              80 

2      3160      99 

820                1-90 

16.75 

33  27*56X52     " 

395            1730 

15    9              80 

I      3244    102 

730                1.92 

15.1 

34  27*56X52     " 

412            1651 

15     9              75  - 

I      3570    102 

771                1.93 

16 

:sr>  2s*60X54d'ble. 

504            4H  K) 

20    0              90 

3      7400    300 

1900                1.96 

40 

36  28*60X54     " 

522            4100 

20     0              80 

J      7413    302 

1850                2.01 

40 

37  16*34X30     " 

360              768 

12    6              68 

L      1350      47.2 

270                2.25 

7 

38  26*52X42     " 

336           2400 

,  17     3              70 

I      3650    132 

900                2.47 

24 

mean  437 

mean  76.  7 

mean  2.026 

39  60&  |  JJj  j-  X66 

605        

21    0            90 

1    19500    780 

6300               1.63 

110 

110  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 

While  Mr.  Marshall's  table  is  of  great  value,  it  must  not  be  forgotten 
that  the  gain  and  rapid  advance  is  due  to  the  increase  of  pressure  and  the 
higher  expansion  used;  and  must  not  be  confounded  with  the  great  gain 
which  resulted  from  the  introduction  of  the  compound  engine  following 
the  surface  condenser.  Of  this  a  portion  was  a  mechanical  one,  due  to 
smoother  action,  and  the  remainder,  the  saving  of  the  heat  lost  by  con- 
stant blowing  off  when  salt  water  was  fed  to  the  boilers. 

Mr.  Marshall  compares  with  a  paper  read  by  Mr.,  now,  Sir  F.  J.  Bram- 
well,  in  1872,  in  which  Mr.  Bramwell  gave  particulars  of  twenty-eight 
steamships. 

The  average  consumption  of  coal  per  indicated  horse-power  per  hour, 
from  nineteen  of  these  vessels,  was  2.11  pounds,  the  steam  pressure  rang- 
ing from  45  to  65  pounds  above  the  atmosphere.  The  steam  averaged,  say. 
52.5  pounds,  and  the  piston  speed  was  376  feet  per  minute. 

We  see  that  the  average  steam  pressure,  was,  in  1881,  77.4  pounds,  the 
average  piston  speed  467  feet,  while  the  coal  consumed  per  indicated 
horse-power  per  hour,  was  1.83  pounds,  or  13.4  per  cent,  less;  and  the  boiler 
surface  is  also  less  per  horse-power.  This  gain  is  shown  to  be  that  theo- 
retically due  to  the  higher  initial  pressure,  the  same  terminal  and  back 
pressure  being  assumed,  the  number  of  expansions  being  in  the  one  case 
5.15,  and  in  the  other  7.05. 

Now  with  steam  of  60  pounds  total  working  pressure,  and  with  4.57  ex- 
pansions, the  theoretical  steam  is  21.93  pounds  per  indicated  horse -power 
per  hour;  for  6  expansions  19.09  pounds,  and  for  8  expansions  18.8  pounds. 
The  difference  between  21.9  and  18.8  =  3.1,  which  shows  the  gain  by  increas- 
ing from  4.57  to  8  expansions. 

The  gain  from  6  to  8  expansions,  or  from  19.1  to  18.8  pounds,  of  steam 
is  only  0.3,  or,  for  7  expansions  say  18.9  pounds;  so  that  we  find  that  most 
of  the  gain  must  come  from  the  increase  in  pressure  and  very  little  from 
the  increase  in  expansion. 

The  value  of  jacketting  and  compounding  is  still  on  open  question. 
For  slow  moving  engines,  both  appear  to  add  to  the  economy;  but  for 
high  speed  engines  little  gain  is  observed.  In  Chapter  V,  in  the  Alsatian 
experiments,  we  shall  find  a  very  strong  argument  in  favor  of  the  single 
cylinder  unjacketed  engine  using  superheated  steam.  In  comparing  the 
economy  of  the  engines  of  the  "Leila,"  using  compound  unjacketed  cylin- 
ders, with  those  of  the  "Siesta,"  we  find  for  the  cases  of  maximum  power 
that  little  was  added  by  the  superheating  but  the  smaller  engine  was 
driven  the  harder.  Looking  at  the  Miller's  Exhibition  engine  we  find 
that  with  the  cylinder  of  the  same  size  it  use^d  but  little  more  steam  per  net 
horse -power, — steam  of  the  same  pressure. 

We  present  here  two  diagrams  from  Porter-Allen  engines.  One 
taken  at  a  trial  using  superheated  steam,  made  at  the  American  Institute 
Fair  in  New  York  several  years  ago,  and  interesting  mainly  as  showing  an 
expansion  curve  similar  to  that  of  steam  in  a  non-conducting  cylinder. 
The  other  is  from  a  compound  engine,  jacketed,  and  with  interheater. 
The  diagrams  then  taken  are  given,  and  also  the  combined  diagram;  the 


o.V  THE  INDICATOR,  ETC.  Ill 


latter  shows  two  curves  of  expansion  for  a  non-conducting  cylinder,  the 
inner  one  for  the  steam  passing  through  the  engine  and  the  outer  one  for 
all  the  steam  used.  A  comparison  of  the  enclosed  areas  with  that  of  the 
outer  curve  shows  the  loss.  We  also  give  illustrations,  and  detailed  draw- 
ings of  some  of  the  principal  features  of  the  Porter- Allen  engine  which  re- 

DlAGBAMS  FROM  PORTER-Al/LBN  ENGINE. 

16"  X  30",  125  revolutions  per  minute. 


Scale 


Record,  1  horse-power  per  25.8  lt>s.  of  water  per  hour 

quire  no  explanation,  see  pages  167  to  187.  They  are  given  as  an  example 
of  the  most  skillful  design  which  has  been  attended  with  the  best  work- 
manship ever  used  in  engine  building. 

We  also  give  illustrations  and  many  details  of  the  Reynolds  Corliss 


112  STEAM  USING;  OR,  8TEAM  ENGINE  PRACTICE. 


Scale  ,'G. 


TO- 


.TO 


40- 


3C 


10 


DIAGRAM  FROM  PORTER-ALLEN  COMPOUND  ENGINE. 

12"  and  21"  X  24",  at  180  revolutions  per  minute. 


COMBINED  DIAGRAM  FROM  PORTER- ALLEN. 
ENGINE. 

Upper  curve  shows  expansion  for  all  steam  used, 
if  in  a  non-conducting  cylinder.  Second  curve 
shows  expansion  for  the  steam  passing  through 
the  cylinders. 

Cylinders  12"  and  21"  X  24"  X  184  revolutions 
per  minute. 


JL\Cul.Ft, 


ON  THE  INDICA  TOR,  ETC. 


113 


engine  biiilt  by  Messrs.  E.  P.  Allis  &  Co.,  of  Milwaukee,  Wis.,  which  were 
kindly  furnished  by  Mr.  Edwin  Reynolds,  and  these  require  no  further 
explanation,  see  pages  153  to  162. 

On  pages  163  to  166  we  also  give  some  illustrations  of  details  of  the 
Lambert ville,  N.  J.,  Iron  Works,  Automatic  Cut-off  Engine. 

The  class  of  engines  with  poppet  valves  we  illustrate  by  some  details 
of  the  engines  of  the  Mississippi  River  Steamboat,  "Montana,"  pages  119  to 
121,  and  an  elevation  of  the  High  Service  Engine,  No.  1,  of  the  St.  Louis 
Water  works,  page  114. 

We  illustrate  herewith  the  action  of  river  engines  by  diagrams  taken 
from  the  Steamboat  "Phil.  E.  Chappel"  and  the  "James  Howard."  A  dia- 


150- 


100- 


DlAGRAM   FROM   LARGE    CYLINDER   OP   ENGINES    OF   RlVER 

STEAMER  "PHIL.  E.  CHAPPEL." 


22  revolutions  per  minute. 


Mean       pressure 
90  and  99  Ibs. 


120 

-100 

80 

60 

40 

-20 

0 


DIAGRAM  FROM  ENGINES  OF  RIVER  STEAMER  "JAS.  HOWARD. 

34&"  X  120"  X  11M"  with  condenser,  12M"  without  condenser. 
1247  I.  H.  P.,  both  engines  with  condenser. 
1268  I.  H.  P.,  both  engines  without  condenser. 


114  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


HIGH    SERVICE    PUMPING     ENGINE, 

No.  I,  St.  Louis,  Mo.,  Water  Works. 

Steam  cylinder  85"  X  120". 


LAWRENCE,  MASS.,  WATER  WORKS. 
May  4,  1876. 

INDICATOR  DIAGRAMS,  UPPER  END. 

High  pressure  cylinder,  18  in.  diameter,  96  in.  stroke. 
Piston  rod,  3.5  in.  diameter.  Volume,  23508  cu.  in.  =  13.6041 
cu.  ft.  Clearance,  601  cu.  in.  =  2.56  per  cent. 

Low-pressure  cylinder,  38  in^ diameter,  96  in.  stroke. 
Piston  rod,  4  in.  diameter.  Volume,  107674  cu.  in.  =  62.1313 
cu.  ft.  Clearance,  1135  cu.  in.  =  1.54  per  cent. 

Difference  of  volume  of  cylinders,  107674  —  23508  =  84,166 
cu.  in. 

Clearance  of  low-pressure  cylinder,  and  difference  of 
volume  of  cylinders,  expressed  in  terms  of  volume  of  high- 
pressure  cylinder,  as  follows: 

1135  -r-  23508  =    .048281  =  4  83  per  cent. 

84166  -7-  23508  =  3.5803. 

Isothermal  curve,  p  *  v.  J 

Adiabatic  curve,  calculated  by  Rankine's  formula, p  <*v   . 

Barometer  corrected  30.099  =  14.78  Ibs.  per  square  inch. 

The  difference  between  the  two  adiabatic  curves  shows 
the  amount   of   water  present   in  the  steam   at   cut-off 
evaporated  by   heat   derived   from  the 
jacket;  and  the  effect  of  the  surface  of 
piston-rods,  acting  as  a   surface   con- 
denser, in  condensing  steam  during  ad- 
mission, to  be  subsequently  ree  vapor  - 
ated.  / 

I  axis  of  Isothermal  curve. 

A  axis  of  Adiabatic  curve. 


— ! —  ,f\y 

_j j 1 j i ;_ .  _  _  _  _  __4__-_.^_-_-_-4-'A|s^ 


5 


g 


The  indicated  work  done  in  smaller  cylinder  may  be  taken  as  including  the  portion 
only  fine  shaded,  in  which  case  the  work  indicated  in  large  cylinder  includes  from  the 
point  A,  the  clearance  being  curved  on  the  indicated  work  in  small  cylinder  is  to  be 
taken  as  including  the  portion  with  coarse  shade,  the  clearance  loss  being  vertical  and 
the  work  indicated  in  long  cylinder  is  that  fine  shaded  only. 

NOTE.— The  Rankine  formula  for  an  adiabatic  curve  is  p  v        =  const.,  and  not 


p  v        =  const.,  as  given  above. 


116 


STEAM  USING;  OH,  STEAM  ENGINE  PRACTICE. 


DIAGRAMS  FROM  ENGINES  OF  S.  S.  "ARIZONA." 


HIGH  PRESSURE. 


90-T 
80- 

10- 

60- 

oO- 
40  - 

ao  - 
20- 

10- 


LOW  PRESSURE. 


COMBINED  DIAGRAM. 

Boiler  pressure  86  Ibs. 

Cylinders,  high  pressure,  60"  X  66"  X  55  revolutions. 
2  low        "  90"  X  66"  X  55 


INDICATED    HORSE-POWER. 


High  pressure  cylinder. 
.FLow 
A     "  "  " 


.2433 
.1925 
.1948 

6306 


ON  THE  INDICATOR,  ETC. 


117 


DIAGRAMS  FROM  ENGINES  OF  THE  S.  S.  "ABERDEEN.' 


70"X  54" 


SINGLE  DIAGRAMS. 


140  e.  /. 

COMBINED   DIAGBAM. 


118  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

gram  is  also  given  on  page  91,  from  the  St.  Louis  Water  Works  engine, 
and  there  is  drawn  thereon  an  expansion  curve  for  the  same  quantity  of 
steam  in  a  non-conducting  cylinder. 

As  illustrating  the  action  of  a  non- receiver  compound  engine  we  give, 
page  115,  a  combined  diagram  from  the  trial  of  the  Lawrence  Pumping 
Engine,  and  have  noted  the  matter  of  indicated  work  thereon, — the  point 
being  that  is  more  than  the. sum  of  the  finely  shaded  areas. 

Single  and  combined  diagrams  are  given  for  the  engines  of  the  S.  S. 
"Arizona,  "the  two  low  pressure  diagrams  combining  as  one  under  the  high 
pressure  diagram;  and  we  also  give  single  and  combined  diagrams  from 
the  triple  expansion  engines  of  the  S.  S.  "Aberdeen,"  see  pages  116,  117. 

As  examples  of  the  exteriors  of  modern  marine  engines  we  have  re- 
produced illustrations  of  the  engines  of  the  steamships  "Grecian,"  the 
"Parisian"  and  the  "Aberdeen,"  see  pages  125  to  129,  which  with  the  above 
diagrams  from  the  "Arizona"  and  "Aberdeen"  are  taken  from  "Engineer- 
ing," of  London. 

We  also  give  illustrations  of  a  compound  engine  of  the  non-receiver 
type,  for  the  U.  S.  Lighthouse  Steamer  "Manzanita,"  pages  122  to  124,  de- 
signed and  built  by  Mr.  H.  A.  Kamsay,  of  the  Vulcan  Iron  Works,  Baltimore, 
Md.  The  "throws"  of  the  two  cranks  are  placed  immediately  opposite  each 
other  or  180°  apart,  and  the  steam  after  doing  its  work  in  the  high  pres- 
sure cylinder,  is  released,  and  passes  at  once  into  the  large  cylinder  when 
the  piston  is  found  at  the  commencement  of  its  stroke  ready  for  the  steam 
to  exert  its  force  upon  it.  Hence  the  interposition  of  a  receiver,  which  is 
required  when  the  cranks  are  placed  at  right  angles  to  each  other,  is  not 
necessary.  The  only  objection  to  the  arrangement  is  the  supposed  greater 
difficulty  in  handling  the  engine  as  both  cranks  are  on  their  dead  centres 
at  one  time,  but  this  is  easily  obviated  by  care  on  the  part  of  the  engineer. 
The  cylinders  are  22  inches  and  36  inches  diameter,  and  the  stroke  of  pis- 
tons is  34  inches.  In  order  to  work  the  valves  with  one  pair  of  eccentrics 
the  valve  faces  are  placed  at  right  angles  to  each  other.  This  arrangement 
simplifies  the  number  of  parts  and  renders  them  easily  accessible  for  ad- 
justment. There  are  no  expansion  or  cut-off  valves  on  either  cylinder  but 
both  which  are  of  the  ordinary  locomotive  type,  are  provided  with  suffi- 
cient lap  to  enable  them  to  suppress  the  steam  at  three -fourths  of  the 
stroke  of  the  pistons.  By  the  proper  arrangement  of  passages  and  valves, 
the  engines  are  arranged  to  work  as  simple  condensing  engines,  compound 
and  high  pressure  or  non-condensing,  as  may  be  desired.  The  surface 
condenser  which  is  of  the  usual  rectangular  cast-iron  box  shape  forms  the 
frame  for  supporting  the  cylinders  on  one  side,  while  the  other  side  is 
supported  on  wrought -iron  columns.  The  air  pump  has  a  trunk  plunger 
and  bucket  actuated  by  wrought-iron  levers  connected  to  the  cross-head 
of  the  low-pressure  cylinder. 

The  condenser  is  arranged  to  pass  the  condensing  water,  furnished  by 
an  independent  steam  pump,  making  three  turns  through  the  condenser. 
The  circulating  pump  has  a  cylinder  of  12  inches  diameter  and  15  inches 
stroke. 


VARIETIES  OF  ENGINES. 


119 


MISSISSIPPI     RIVER    STEAMER    "MONTANA." 
Cylinder  and  Valves. 


A 


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120  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


DETAILS. 
Scale,  M  inch  =  1  foot. 


Cutoff  Cam. 

MISSISSIPPI     RIVER    STEAMER    "MONTANA.' 


VARIETIES  OF  ENGINES. 


121 


ENGINES    OF    THE    U.    S.    LIGHTHOUSE 
STEAMER    "MANZANITA." 


ELEVATION. 


VARIETIES  OF  ENGINES. 


123 


ENGINES    OF    U.    S.    LIGHTHOUSE    STEAMER    "  MANZANITA." 


PLAN. 


ENGINES    OF    U.    S.    LIGHTHOUSE    STEAMER    "  MANZANITA.' 


ELEVATION. 


VARIETIES  OF  ENGINES. 


125 


TRIPLE-EXPANSION     ENGINES    OF    S.   S.    "ABERDEEN.1 


PERSPECTIVE  VIEW. 
Cylinders  30",  45"  and  70"  X  54"  stroke. 


COMPOUND    ENGINES    OF    S.    S.    "GRECIAN." 


SIDE    ELEVATION. 
Cylinders  48"  and  84"  X  54"  stroke.    2000  horse  power. 


VA  EIETIES  OF  ENGINES. 


127 


COMPOUND    ENGINES    OF    S.    S.    "GRECIAN. 


END  ELEVATION. 


128 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


THREE-CYLINDER    COMPOUND    ENGINE    OF    S.    S.    "PARISIAN.' 


Cylinders  60",  85"  and  85"  X  60"  stroke. 


VARIETIES  OF  ENGINES. 


129 


THREE-CYLINDER    COMPOUND    ENGINES    OF    S.    S.    "PARISIAN." 


13O  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

On  pages  138  and  139  will  be  found  illustrations  of  the  engines  of  the 
steam  yacht  "Leila,"  built  by  the  Herreshoff  Manufacturing  Company, 
Providence,  B.  I. 

The  Buckeye  engine  we  illustrate  in  detail,  see  pages  141  to  152.  It 
appears  at  first  sight  to  have  only  an  expansion  valve  on  the  back  of  the 
main  slide,  with  the  change  in  the  cut-off  given  by  the  rotating  weights 
on  the  shaft  turning  the  expansion  eccentric  round  the  shaft.  But  the 
connection  between  the  expansion  eccentric  and  its  slide  is  through  a  rock- 
ing lever  with  equal  arms,  carried  at  its  centre  at  the  middle  of  a  rocking 
lever  pivotted  at  the  lower  end.  The  effect  of  this,  while  throwing  the 
expansion  slide  to  the  other  side  of  the  main  slide,  is  also  to  render  the 
movement  of  the  expansion  slide  on  the  back  of  the  main  slide  entirely 
independent  of  the  position  of  the  latter;  for  the  expansion  slide  is  in 
its  central  position  on  the  main  slide  when  the  two  working  levers  are 
in  line,  which  only  requires  the  expansion  eccentric  to  be  in  a  given 
place.  The  arrangement  is  therefore  as  if  the  expansion  slide  worked  on 
a  fixed  seat,  dividing  the  steam  chest,  with  the  advantage  of  a  very  small 
clearance. 

In  drawing  the  valve  diagram  we  find  from  the  distance  circle  for  the 
main  valve,  the  points  of  admission,  release  and  cushion;  but  we  draw 
either  on  the  same,  or  a  separate  diagram,  the  distance  circle  for  any  posi- 
tion of  the  expansion  eccentric,  and  remembering  the  lap  is  negative,  we 
draw  the  lines  for  the  opening  and  closing  of  the  ports  in  the  slide  by  the 
expansion  slide. 

By  turning  these  round  from  the  place  where  the  cut-off  is  made  by 
the  main  slide  to  any  early  limit  desired,  the  range  and  throw,  or  range  and 
lap,  may  be  determined.  This  presents  no  difficulty,  and  is  simpler  than 
the  case  of  the  common  engine  in  which  the  expansion  eccentric  is  also 
turned  round  the  shaft. 

On  page  136  we  give  an  illustration  and  description  of  the  Steam 
Engine  Governor  used  by  the  Cummer  Engine  Company,  of  Cleve- 
land, O. 

Four  port  engines  are  the  oldest  type  of  vertical  engines  with  poppet 
valves,  and  the  lifting  is  usually  performed  by  cams.  The  first  attempt  at 
expansion  was  made  by  Stevens.  The  rock  shaft  holding  the  cams  was 
moved  by  a  rod  from  the  eccentric;  the  end  of  the  rock  shaft  carried  an 
arm  with  a  pin  thereon  and  the  rod  from  the  eccentrics,  passing  on  this  pin, 
was  slotted.  By  using  a  large  eccentric,  set  much  in  advance,  this  rod  ac- 
quired considerable  motion  in  either  direction  before  the  rock  shaft  was 
put  in  motion,  a.nd  the  opening  of  the  valves  was  made  much  more  rap- 
idly. As  the  cams  could  move  down  without  any  effect  after  the  valve  had 
seated,  the  closure  was  made  earlier  and  also  more  promptly.  A  drop  cut 
off  was  afterwards  devised  by  Sickles,  and  the  steam  valve  stems  were 
lifted  by  clutches  and  released  at  any  point  desired.  This  gear  could  be 
altered  by  hand  while  running.  Pumping  engine,  No.  1,  High  Service, 
St.  Louis  Water  Works,  has  been  given  as  a  good  example  of  this  kind  of 
machine. 


VARIETIES  OF  ENGINES.  131 

The  credit  of  the  Automatic  cut-off,  or  expansion  varied  by  the  gov- 
ernor, must  be  accorded  to  Geo.  H.  Corliss,  of  Providence,  Khode  Island. 
He  introduced  a  four  port  engine  with  twisting  valves,  adding  various  de- 
vices in  the  way  of  connections  and  adjustments,  until  he  secured  a  very 
rapid  opening  of  the  steam  valve,  and  rapid  opening  and  closing  of  the 
exhaust  valves.  The  latter  were  permanently  attached  to,  and  moved  by, 
the  eccentric,  and  only  by  moving  the  eccentric  of  the  shaft  and  by  chang- 
ing the  length  of  the  rods  can  any  change  be  produced  in  their  movement. 
The  steam  valves  were  lifted  by  clutches,  which  met  with  a  releasing  piece 
at  some  point  of  the  opening  determined  by  the  governor,  the  earlier  the 
faster;  the  mean  effective  pressure  in  the  cylinder  is  thereby  reduced,  the 
speed  lowers  and  is  again  increased.  By  a  delicate  governor  these  vari- 
ations may  be  made  almost  imperceptible. 

The  undoubted  gain  made  by  these  engines  in  the  use  of  steam,  is  due 
to  the  fact  that  the  initial  pressure  up  to  the  cut  off  is  kept  nearly  that  of 
the  boiler,  and  that  with  the  large  ports  and  quick  opening  valves  the 
back  pressure  is  reduced  to  the  least  possible  amount.  The  piston 
speed,  number  of  revolutions,  and  steam  pressure  are  all  increased  while 
the  clearance  is  very  greatly  reduced.  And,  in  fact  the  gain  is  due  to  a 
general  fitness  and  skillful  combination  of  things,  all  of  which  were 
good  in  themselves,  and  which  in  no  way  disturbed  each  other,  when 
combined. 

The  closing  of  the  steam  valves  after  being  tripped  has  been  caused 
by  weights,  by  springs,  by  compressed  air,  by  air  of  reduced  pressure,  and 
by  steam,  as  well  as  by  combinations  of  these  forces.  The  best  results 
have  been  given  in  this  country  by  weight  and  vacuum  tending  to  close 
the  valve,  with  an  air  dash  pot  to  take  up  the  shock. 

At  the  expiration  of  the  patents  covering  Mr.  Corliss'  improvements, 
a  number  of  builders  commenced  making  engines  of  almost  exactly  the 
same  pattern.  Of  these  imitations  which  contain  very  many  improve- 
ments, perhaps  those  built  by  Mr.  Wm.  A.  Harris,  of  Providence,  are  best 
known  in  the  East,  while  those  of  Messrs.  E.  P.  Allis  and  Co.,  of  Milwaukee, 
working  from  the  designs  and  under  the  supervision  of  Mr.  Edwin  A. 
Reynolds,  have  suited  the  requirements  of  the  Western  practice. 

To  take  an  example  of  a  four- port  engine  with  poppet  valves  we  select 
the  western  river  Steamer  "Montana,"  given  on  pages  119  to  121.  The  four 
valves  are  moved  by  four  cams  from  two  rock  shafts,  driven  by  rods  from 
triangular  cams  on  the  shaft.  The  engines  can  be  worked  by  hand  or  not, 
at  full  stroke,  backward  or  forward,  and  at  a  fixed  cut-off  never  earlier 
than  one-half  stroke  while  running  forward. 

A  single  cam  on  the  shaft  connected  to  the  steam  rock  shaft  is  used  for 
the  cut-off,  while  the  exhaust  side  rockshaft  is  driven  by  the  other  cam. 
To  use  full  stroke  this  is  disconnected  and  the  two  rockshafts  hooked  to 
work  together  from  the  exhaust;  while  to  reverse,  the  full  stroke  cam  is 
hooked  to  the  rock  arm  driving  the  exhaust  on  the  other  side.  The  rapid 
movements  of  the  valves  in  opening  and  closing  are  seen  from  the  dia- 
grams taken  from  the  steamer  "Phil.  E.  Chappel."  Two  cards  are  given 


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VARIETIES  OF  ENGINES.  133 

from  the  "James  Howard"  shown  with  and  without  the  use  of  the  con- 
denser. The  condenser  was  opened  to  the  cylinder  after  the  bulk  of  the 
steam  had  been  exhausted  into  the  air,  say  when  the  piston  had  moved 
one- tenth  of  the  stroke  backwards,  the  increase  of  pressure  found  was 
about  ten  pounds  or  10  per  cent.,  and  the  great  size  of  condenser  and  air 
pump  were  reduced  because  little  of  the  steam  was  left.  It  was  found 
practically  that  the  increase  of  the  range  of  temperature  between  the  in- 
coming and  outgoing  steam  was  enough  to  so  increase  the  internal  waste 
that  no  economy  but  a  positive  loss  was  attendant  upon  its  use. 

Following  the  Corliss  type  of  engine  closely  is  that  of  Mr.  Jerome 
Wheelock,  of  Worcester,  Mass.,  which  is  however,  only  two-ported.  The 
valves  are  of  the  Corliss  pattern  and  two  are  used  for  opening  to  steam  and 
for  opening  and  closing  the  exhaust.  The  closing  of  the  steam  is  governed 
by  two  other  valves  of  the  same  kind  placed  upon  the  steam  passage 
leading  to  the  main  valves,  and  moved  from  the  main  valves  by  clutch 
links  which  are  tripped  by  the  governor.  This  engine  has  a  future,  but  as 
built,  it  leaves  a  separate  eccentric  for  the  steam  and  exhaust  valves,  and 
a  general  increase  in  strength,  to  be  desired.  The  use  of  two  eccentrics, 
one  for  the  steam,  and  one  for  the  exhaust,  valves,  has  been  followed  in 
this  country  by  the  Atlas  Engine  Works,  of  Indianapolis,  and  is  generally 
desirable.  One  of  the  best  frames  made  with  the  Corliss  engine  has  been 
a  modification  of  that  used  by  Wm.  Wright,  in  his  four-port  slide  valve 
engines  and  has  been  adopted  by  Messrs.  Smith,  Beggs  &  Kankin,  of  St. 
Louis. 

The  Porter- Allen  engine  is  a  four-port  slide  valve  engine  with  steam 
slides  balanced  and  worked  from  a  link,  the  position  in  the  link  of  the 
radius  rod  attached  to  the  valve  stem  being  controlled  by  the  governor; 
the  balanced  exhaust  valves  are  worked  from  some  fixed  part  of  the  link. 
The  engine  is  intended  to  run  at  high  speed  both  in  revolutions  and  pis- 
ton travel,  and  on  this  engine  was  first  studied  and  developed  the  actual 
effect  of  the  weight  of  the  reciprocating  parts  of  the  engine,  the  piston, 
rod,  cross -head  and  connecting  rod.  These  pieces  evidently  have  to  be 
started  on  the  stroke  before  any  pressure  from  the  steam  can  reach  the 
crank  pin  and  main  journal,  and  if  they  are  heavy  and  the  speed  high,  al- 
most all  the  pressure  of  the  steam  upon  the  piston  may  be  absorbed  in 
starting  this  dead  weight.  In  any  case  the  full  force  of  the  steam  acting 
upon  the  piston  is  reduced  before  it  reaches  the  crank  pin.  After  the  en- 
gine has  passed  mid  stroke  where  this  weight  is  now  moving  at  its  great- 
est speed  we  find  that  the  steam  pressure  has  very  much  fallen  if  the  cut- 
off be  early,  and  that  the  inertia  of  the  moving  parts  is  now  pressing  with 
the  steam  pressure  against  the  crank.  Thus  the  weight  of  the  moving 
pieces  tends  in  connection  with  the  varying  cylinder  pressures  to  equal- 
ize the  pressure,  wear,  and  rotation. 

In  some  cases  we  have  examined  we  found  that  the  load  on  the  engine 
was  so  light  and  the  boiler  pressure  so  low,  the  cut-off  taking  place  early. 
Under  these  conditions  the  crank  pin  was  started  entirely  by  the  fly  wheel 
and  the  crank  pin  actually  dragged  from  one  end  the  weight  which 


134  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

the  steam  was  pushing  at  the  other.  At  mid  stroke  the  steam  pressure 
had  fallen  considerably  and  the  inertia  of  the  weight  now  moving  fast  did 
all  the  work  from  there  to  the  end  of  the  stroke.  This  of  course  is  not  de- 
sirable, but  it  may  be  considered  that  to  have  half  the  initial  pressure 
transmitted  to  the  pin,  while  half  is  taken  up  in  moving  the  weight  to  be 
given  out  again  at  the  end  of  the  stroke,  is  the  best  adjustment  possible. 


THE    RIDER    AUTOMATIC    EXPANSION    GEAR. 


VARIETIES  OF  ENGINES.  135 

This,  of  course,  can  only  be  done  for  one  speed  and  steam  pressure  by 
properly  designing  the  weight,  and  average  results  only  can  be  reached. 
This  action  combined  with  the  high  rotation  speed  on  the  fly  wheel 
causes  these  engines  to  run  with  what  appears  to  be  a  simply  marvelous 
smoothness,  and  the  quick  acting  governor  maintains  the  speed,  chang- 
ing in  height  under  variations  of  revolution  which  are  too  small  to  be 
otherwise  noticed.  Illustrations  of  this  engine  are  given  on  pages  167 
to  187. 

Among  stationary  engines  in  England,  by  far  the  most  common  type  is 
that  of  a  slide  valve  with  an  expansion  slide  on  the  back,  and  it  is  the  most 
common  type  in  Europe.  The  arrangement  is  very  often  used  with  small 
engines,  as  small  as  those  with  8  inch  cylinders,  without  means  of  vary- 
ing the  expansion,  and  with  the  speed  regulated  by  a  throttle  and  govenor 
as  usual.  In  the  United  States,  on  the  other  hand,  this  form  (non-adjus- 
table) is  rarely  to  be  met  with.  While  the  use  of  an  expansion  slide 
varied  by  hand  is  by  no  means  common,  a  very  neat  type  is  made  at 
Erie,  Pa.,  of  the  class  in  which  the  negative  lap  is  varied  by  a  right 
and  left  hand  screw  and  hand  wheel  projecting  from  the  end  of  the  steam 
chest.  By  this  wheel  the  expansion  can  be  changed  while  the  engine  is 
running. 

One  of  the  neatest  automatic,  or  governor,  expansion  gears,  is 
that  of  Eider,  of  the  Delamater  Iron  Works,  New  York  City.  The  back  of 
the  main  slide  is  hollowed  into  a  part  of  a  cylinder  whose  axis  is  the  centre 
of  the  expansion  slide.  The  lap  edges  of  the  expansion  slide  and  steam 
edges  of  main  slide  are  tapered  in  such  a  manner  that  by  rotation  of  the 
expansion  slide  the  lap  is  changed  as  in  the  ordinary  manner.  This  rota- 
tion is  accomplished  by  a  spindle  attached  to  the  govenor,  gearing  into  a 
sector  on  the  valve  stem. 

When  an  expansion  slide  is  used  in  connection  with  a  link  motion  for 
the  main  valve,  in  many  cases  the  expansion  slide  is  driven  by  its  eccen- 
tric set  opposite  the  crank,  and  change  of  cut-off  is  given  by  change  of  lap 
and  a  right  and  left  hand  thread  and  handwheel.  In  such  cases  the  link 
is  usually  worked  full-gear  only,  and  the  cut-off  applied  after  the  engine 
is  in  motion.  The  lap  is  negative. 

A  more  common  form  with  large  engines,  where  the  weight  becomes 
harder  to  handle,  is  to  cut  into  two  parts  the  expansion  valve  rod  and  to 
connect  one  of  them  to  a  link,  making  the  other  a  radius  rod  pinned  to  the 
valve  stem,  and  working  with  slides  in  the  link.  The  position  of  the 
slider  in  the  link  is  determined  by  a  screw  and  handwheel.  Thus  a 
change  of  travel  is  effected  in  the  expansion  valve.  The  diagram  is 
readily  constructed,  and  the  results  are  good,  but  the  steam  chest  has  to 
be  made  longer  than  would  be  otherwise  required. 

A  more  complex  arrangement  is  found  in  some  cases  with  the  link 
motion,  a  third  eccentric  and  second  link  being  added.  The  second 
link  is  attached  to  the  expansion  eccentric  at  one  end  and  the  main 
valve  stem  at  the  other.  The  expansion  slide  is  moved  by  its  valve 
stem,  and  either  by  a  radius  rod  and  link  curved  to  fit  the  radius 


VMUET1KS  Of-'  K \irIXES.  137 

rod,  or  by  a  double  curved  link.     This    combination  of  links  can  be 
sketched  as  follows : 

A  is  the  crank,  and  C  the  shaft  centers.    B,  D,  and  E  are  the  virtual 
centers  of  the  three  given  eccentrics,  while  F  is  the  virtual  eccentric  for  a 

given    position  of 
the  main  link,  and 
G.  on  E  F,  dividing 
J?  it  as  the  expansion 

_._  _  _  slider  divides  the 

-1   - 


second  link,  is  the 
virtual  eccentric 
driving  the  expan- 
sion slide. 

The  diagram 
for  the  cut-off  is 
then  readily  constructed  from  these  two  virtual  eccentrics  by  the  ordinary 
methods. 

The  use  of  this  class  has  been  confined  as  far  as  we  are  aware  to  the 
beautiful  marine  engine  of  Messrs.  Herreshoff,  of  Bristol,  K.  I. 

An  automatic  engine  built  under  patents  of  Messrs.  Armington  & 
Simms  is  a  good  example  of  neat  and  careful  design.  The  engine  is  worked 
by  a  piston  valve,  and  the  governor  is  like  that  of  the  Buckeye  and  many 
other  engines,  a  pair  of  weights  attached  to  the  main  shaft.  But  in  the 
Buckeye  the  governor  acts  only  on  the  expansion  valve  eccentric,  pulling 
it  ahead  on  the  shaft  if  the  speed  is  increased.  In  the  Armington  &  Simms 
engine  the  pair  of  weights  flying  out  pull  on  what  may  be  called  a  compound 
eccentric.  This  compound  eccentric  is  the  peculiar  feature  of  the  engine; 
the  ordinary  eccentric,  loose  on  the  shaft,  carries  instead  of  the  usual 
strap,  a  second  eccentric  with  about  one  third  the  arm  of  the  first.  The 
weight  is  a  heavy  casting,  pivoted  at  one  end  to  the  governor  disc;  at  the 
free  end  it  is  connected  to  the  lugs  on  the  inner  eccentrics,  and  at  its  mid- 
dle to  the  outer  eccentric,  but  on  the  other  side  of  the  shaft,  the  result 
being  that  the  eccentrics  are  pulled  around  the  shaft  in  opposite  direc- 
tions. The  effect  is  that  the  outer  eccentric  centre  changes  both  in  angle 
and  in  arm,  very  much  as  it  is  varied  in  a  more  simple  manner  in  the 
Westinghouse  automatic  engine,  already  illustrated.  The  rest  of  the  en- 
gine requires  no  comment. 

With  large  cylinders  the  valves  become  large,  but  while  the  steam 
port  edge  which  regulates  admission  increases  with  the  diameter,  the 
volume  to  be  filled  varies  with  the  square  of  the  diameter.  And  in  order 
to  give  length  enough,  the  only  way  it  can  be  increased,  the  edges  are 
often  doubled,  or  the  body  of  the  value  cored  with  passages  to  the  exhaust, 
while  steam  is  admitted  from  the  sides  of  the  value  to  the  additional  ports. 
When  the  cylinders  are  large  these  valves  become  very  complicated,  and 
are  matters  of  special  study. 

Locomotive  and  portable  engines  assume  special  forms  but  the  only 
real  difference  is  that  boiler  and  engines  have  to  be  so  attached  as  to  move 


138  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


ENGINES    OF    THE    STEAM    YACHT    "LEILA.' 


SIDE   VIEW. 
Cylinders  9"  and  16"  X  18". 


VARIETIES   OF  E\<;IXK*. 


139 


ENGINES    OF    THE    STEAM    YACHT    "LEILA." 


END  VIEW. 


140  STEAM  USING;   OR,  STEAM  ENGINE  PEACTICE. 

together.  The  locomotive  has  always  two  cylinders,*  operating  upon 
cranks  at  right  angles,  and  carried  on  from  four  to  twelve  wheels,  of 
which  from  two  to  twelve  have  the  same  diameter  and  are  coupled  to- 
gether thus  acting  as  driving-wheels.  The  remaining  wheels  are  smaller 
and  act  only  as  bearing  wheels.  The  wheels  are  set  with  bearings  in  a 
frame  to  which  the  cylinders  are  firmly  connected.  Upon  this  frame  is  set 
the  boiler  and  its  appurtenances.  The  water  and  fuel  are  carried  in  some 
forms  upon  this  frame,  but  more  usually  upon  a  separate  frame  and  wheels 
called  the  "tender." 

The  engine  proper  is  the  pair  of  cylinders  with  their  connections  to 
the  wheels  and  the  valve  gear  back  from  the  wheels  to  the  steam.  The 
valve  is  almost  always  the  three  ported  slides  driven  by  a  link  motion,  and 
there  is  no  difference  whatever  in  the  use  of  steam  in  the  engine  itself  from 
any  other  engine  of  the  same  type.  The  number  of  revolutions  is  at  times 
high,  and  the  piston  speed  great,  but  the  engine  is  rarely  kept  at  hard 
work  for  more  than  an  hour  at  a  time. 

Cylinders  are  used  up  to  24  inches  in  diameter  while  the  stroke  is  rarely 
over  26  inches.  A  few  engines  for  the  Central  Pacific  Railway  have  a  30- 
inch  stroke,  and  have  an  expansion  slide  on  the  back  of  the  main  slide, 
but  such  engines  have  been  tried  before  and  the  only  gain  is  likely  to  be 
that  due  clearance,  for  at  slow  speeds  and  late  cut-off  the  expansion  valve 
adds  nothing;  while  at  high  speed  and  early  cut-off  the  cushion  produced 
by  the  link  motion  and  single  slide  is  found  to  be  essential  in  reducing 
shock  and  increasing  durability.  And  it  may  be  safe  to  say  that  no  other 
than  the  single  slide  in  some  of  its  forms,  driven  by  the  link  or  kindred 
motion,  is  likely  to  be  used;  for  in  spite  of  many  attempts  to  improve  it, 
George  Stephenson  left  the  locomotive  as  it  still  remains  in  all  essential 
points,  and  that  the  only  improvement  worth  noting  is  the  addition  of  the 
automatic  air  brake  which  may  be  called  the  most  important  adjunct  to 
railway  train  service  after  the  locomotive. 

The  varieties  of  engines  and  cut-off  gear  are  almost  endless,  but  we 
have  endeavored  to  restrict  ourselves  to  the  ordinary  and  well-defined 
successful  constructions.  New  patterns  are  being  used  every  day,  and  we 
have  omitted  a  number  of  beautiful  and  apparently  successful  forms, 
manufactured  by  well-known  builders,  wholly  because  they  have  only 
been  in  operation  for  a  comparatively  short  time. 

*The  London  and  Northwestern  Bailway,  England,  have  built  a  number  with  three 
cylinders  which  have  been  very  successful,  and  the  Boston  and  Albany  is  building  one 
with  four  cylinders,  both  of  these  cases  being  compound  engines.  Mr.  Fairlie  and  others 
have  built  locomotives  with  four  cylinders,  which  were,  however,  properly  speaking, 
duplex  locomotives. 


H-  a 

o  g 

p  § 

<  ^ 

o  S 


VARIETIES  Of1  ENGINES. 


143 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 


144  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 


THE  BUCKEYE  ENGINE  COMPANY'S  ISOCHRONAL  REGULATOR. 


EXPLANATION. 

Two  levers,  a  a,  are  pivoted  to  the  arms  of  the  containing  case  at  one  of  their  ends 
as  at  6,  while  the  movable  ends  are  connected  by  links  B  B,  to  ears,  or  flanges,  on  the 
sleeve  of  the  loose  eccentric,  C,  so  that  their  outward  movement,  in  obedience  to  cen- 
trifugal force,  as  indicated  by  dotted  lines,  advances  the  eccentric  forward  in  the  direc- 
tion of  revolution.  Springs,  F  F,  of  tempered  steel  wire,  furnish  the  centripetal  force. 
The  tension  of  the  springs  is  adjusted  by  a  screw  at  c.  The  proper  speed  is  obtained  by 
adding  more  or  less  weight  at  A,  or  within  certain  limits  by  shifting  the  weights  along 
the  levers.  The  case,  which  is  made  in  halves,  is  clamped  to  the  shaft  by  pinch  bolts,  a- 
The  spring  clips,  d,  are  adjustable  along  the  levers.  The  parts  are  shown  in  their 
proper  position  for  motion  in  the  direction  of  the  arrow;  for  motion  in  the  opposite 
direction,  the  levers  are  pivoted  to  the  other  arms  of  the  case  and  the  springs  are 
reversed. 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 


GENERAL  DETAILS. 


a,  Bock  Shaft.  &  &,  Adjustable 
Bearings.  A,  Main  Bock  Arm. 
6  6,  Clamping  Bolts.  C  D,  Arms 
of  Cut-off  Bock  Shaft,  B,  actu- 
ated by  Cut-off  Eccentric  Bod  at 
E.  H,  Hole  for  Starting  Bar. 


CROSS  SECTION  OF  BED  AND  COMPOUND  BOCK  AKM. 


&,  Gun-metal  Spool  in  halves,  a.  Pin.  c, 
Bolt,  d,  Handle  continued  in  a  threaded 
spindle,  which  bites  into  spool,  6,  and  takes 
up  lost  motion . 


BALL  AND  SOCKET 
JOINT  OF  GOVER- 
NOR LINK. 


PINCH  WRIST. 

c,  Wrist  clamped  to  stem,  6,  by  bolt,  a. 


a,  Ball-headed  Stud,  d,  Head  of 
Link.  &,  Hardened  steel  button. 
c,  Cap,  to  screw  down  solid. 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 
GENERAL  DETAILS. 


BALL,  AND  SOCKET  JOINT  IN  CUT-OFF 
VALVE  STEM. 

&,  Sleeve  Nut  screwing  over  head  of  stem 
d,  jammed  by  Sleeve  Nut  c.  e,  Clamp  Han- 
dle set  at  about  45°. 


CROSS  HEAD  FOE  GIBDEB  BED  TYPE. 

Cross-head  is  in  halves,  pinched  on  the 
thread  of  piston  rod,  a,  by  bolts,  //.  &,  Pin. 
c  c,  Tongue  Gibs,  d,  Wedges,  e  e,  Screws. 


DEVICE  FOR  OILING  CRANK  PIN. 

c,  Hole  in  Crank  Pin.  b,  Tube  communicating 
with  c.  a,  Ball  to  receive  oil ;  a,  being  stationary, 
the  oil  is  fed  into  tube  by  the  centrifugal  force. 


AUTOMATIC  WASTE  COCK. 


VARIETIES  0^  ENGINES. 


147 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 
SOME  DETAILS  OF  A  20"  x  40"  ENGINE. 


Edge  of  foot    -»j  | 


CYLINDER. 


CYLINDE3  HEADS. 


148  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 
SOME  DETAILS  or  A  20"  X  40"  ENGINE. 


VALVES. 


VALVE  CHEST  COVEK,  ETC. 


VARIETIES  OF  ENGINES. 


149 


THE    BUCKEYE    AUTOMATIC    CUT-OFF 

SOME  DETAILS  OF  A  20"  X  40"  ENGINE. 


^iJFO; 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 
SOME  DETAILS  OF  A  20"  x  40"  ENGINE. 


Of=  ~*£E1 

TZ-^rrU-^---  =tm\-  PT~ 
X, 3 — if^JWTS  f JT 


VARIETIES  OF  ENGINES. 


151 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 


SOME  DETAILS  or  A  20"  x  40"  ENGINE. 


.    -.  K^J     -»4S 

±^£_p 


SPLIT  ECCENTRICS. 


152 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


THE    BUCKEYE    AUTOMATIC    CUT-OFF    ENGINE. 

SOME  DETAILS  OF  A  20"  x  40"  ENGINE. 


BED   PLATE. 


CONNECTING   KOD. 


-^ 


156 


STEAM  USING;  OR,  STEAM  ENGINE  PH. ACTIVE. 


VARIETIES  OF  ENGINES. 


167 


THE    REYNOLDS'    CORLISS    ENGINE. 


— **%• *j 


END  VIEW  OF  CYLINDER,  ETC. 
Showing  arrangement  of  Valve  Gear  for  20"  X  48"  Engine. 


158  STEAM  USING;  OH,  STEAM  ENGINE  PRACTICE. 


THE    REYNOLDS'    CORLISS    ENGINE. 

-SSF 


Valve        -1 1 $ t _i _-A'--~-  - : 


4ftgg»t  Valve  Stem  tf%"Long 


*~£  -  Exhaust,  V_alyeSie?rLl5*/8'%Q?ia_^ 
Exhaust  Bonnet  2  of  this     \ 


4  of  this 


VALVES,  ETC.,  FOE  A  20"  X  48"  ENGINE. 


VARIETIES  OF  ENGINES. 


THE    REYNOLDS'    CORLISS    ENGINE. 

Ki: 


DETAILS  OF  VALVE  GEAR,  ETC. 
FOE  A  20"  X  48"  ENGINE. 


160 


STEAM  USING;   OR,  STEAM  ENGINE  PRACTICE. 


THE    REYNOLDS'    CORLISS    ENGINE. 


DETAILS  OF  GOVERNOR,  ETC. 

For  a  20"  X  48"  Engine. 


VARIETIES  OF  ENGINES. 


THE    REYNOLDS'    CORLISS    ENGINE. 


•>"«        .  ^  i    ,    ' '  ''V  _  '  *.  i  n  1  \      i '.'.".'    <    * 


-— i-;.^  r —    — | *• — f— 

u-^-t-- J       J l^L ! 1 


162 


UTEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


THE    REYNOLDS'    CORLISS    ENGINE. 


II 
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THE    LAMBERTVILLE,     N.    J.,     IRON     WORKS     PATENT     AUTOMATIC 
CUT-OFF    ENGINE. 


VIEW  OF  GOVERNOR  AND  SECTION  THROUGH  BED. 


LAMBERTVILLE,    N.    J.,    IRON    WORKS 

PATENT    AUTOMATIC    CUT-OFF 

ENGINE. 


GOVERNOR— SIDE  VIEW. 


\ 


168  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

THE    PORTER-ALLEN    ENGINE. 


VERTICAL  CROSS  SECTION  THROUGH  CYLINDER  AND  VALVES 


SECTIONAL  PLAN  OF  CYLINDER  THROUGH  STEAM  AND  EXHAUST  VALVES, 


VARIETIES  OF  ENGINES. 


169 


THE    PORTER-ALLEN     ENGINE. 


SIDE  AND  FRONT  ELEVATION  OF  ECCENTRIC  AND  LINK. 


ELEVATION  AND  PLAN  OF  VALVE  CONNECTIONS. 


THE    PORTER-ALLEN     ENGINE. 


PLAN  AND  ELEVATIpN  OF  MAIN  SHAFT  BEARING. 


i 

ijy 


CEOSS-HEADS. 


VARIETIES  OF  ENGINES. 


171 


THE    PORTER-ALLEN    ENGINE. 
CRANK  PIN  OILER. 


CENTRE  LINE  OF  SHAFT. 


IMM  Ml 


it  it  i  I  I  in  i  i  in 


174 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


VARIETIES  OF  ENGINES. 


q 

UUJ 


175 


176  STEAM  USING;   OR,  STEAM  ENGINE  PRACTICE. 


THE    PORTER-ALLEN     ENGINE. 


f 


PLAN  OF  COMPOUND 
CONDENSING  ENGINE. 


VARIETIES 


>  OF  ENGINES.  *  ' 

L     ""  ~"      """" 


177 


VARIETIES  OF  ENGINES. 


i 


180 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE, 


THE 

PORTER-ALLEN 
ENGINE. 


DETAILS    OF 
COMPOUND  CON- 
DENSING   ENGINE. 


VARIETIES  OF  ENGINES. 


183 


C  Line  of  Cylinder 


Section  on  Line  B  B 
(See  previous  page.) 


Section  through  A  A 
(See  previous  page.) 


THE    PORTER-ALLEN    ENGINE. 
DETAILS  FOR    A   11^"   X   20"   ENGINE 


THE    PORTER-ALLEN     ENGINE. 
DETAILS  OF  CYLINDER  AND  VALVES  FOR  llh>"  X  20"  ENGINE. 


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THE    PORTER-ALLEN     ENGINE. 
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186 


STEAM  USING;   OR,  STEAM  ENGINE  PRACTICE. 


THE    PORTER-ALLEN     ENGINE. 


DETAILS   OF  GOVERNOR  FOR  11 V    X  20' 
ENGINE. 


VARIETIES  OF  ENGINES. 


187 


THE    PORTER-ALLEN     ENGINE. 


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DETAILS  OF  MAIN  BEARINGS  FOR  A  11?2"  X  20"  ENGINE. 


CHAPTER     V.* 

THE     ALSATIAN     EXPERIMENTS— THE     WORK    OF     MESSRS.     HIRN    AND 

HALLAUER. 

KEPORT  ON  A  MEMOIR  PRESENTED  BY  M.  O.  HALLAUER,  UPON  "STEAM 
ENGINES."    BY  M.  KELLER. 

The  work  of  M.  Hallauer  is,  as  its  title  suggests,  a  study  of  the  economic 
influence  of  the  degree  of  expansion  (point  of  cut-off)  in  various  types  of 
steam  engines.  It  tends  also  to  support  by  analyses,  more  and  more 
numerous,  the  conclusions  of  the  last  paper  of  the  author— the  equality  in 
the  matter  of  industrial  consumption  of  simple  and  compound  engines, 
the  advantage  being  rather  on  the  side  of,the  former. 

It  is  divided  into  three  parts:  the  first  comprises  researches  relative  to 
double  cylinder  engines;  the  second  concerns  single  cylinder  engines, 
and  the  third  sums  up  and  compares  the  results  obtained.  We  will  follow 
M.  Hallauer  successively  in  the  order  adopted  by  him  in  the  study  which 
occupies  us,  viz.,  first,  the  compound,  then  the  simple  engines,  and,  sum- 
ming up  for  each  type,  we  will  conclude  upon  the  whole  work. 

FIRST   PART. — DOUBLE    CYLINDER    ENGINES,    KNOWN   AS    "  WOOLF,"   OR 

COMPOUND. 

M.  Hallauer  states,  first,  all  that  has  been  said  concerning  the  ad- 
vantages of  this  system,  and  after  discussion  arrives  at  the  conclusion 
that  the  only  really  serious  consideration,  "a  priori,"  which  cannot  be 
gainsaid,  and  which  stands  in  its  favor,  is  this: 

That  the  difference  of  force  at  the  commencement  and  at  the  end  of 
the  stroke  is  smaller  than  for  other  types  of  engines,  and  that,  in  conse- 
quence of  this  better  distribution  the  running  of  the  machine  is  much 
smoother.  In  regard  to  the  useful  effect  of  the  compound  engine,  the 
brake  experiments,  executed  under  the  auspices  of  your  mechanical  com- 
mittee, have  shown  that  the  "Woolf "  engines  absorb  more  force  in  them- 
selves than  single  cylinder  engines,  a  result  easily  foreseen. 

Passing  then  to  the  study  of  the  influence  of  the  cut-off  in  the  small 
cylinder,  M.  Hallauer  commences  by  verifying  the  results  obtained: 

First.  In  a  series  of  experiments  executed  by  himself  in  1877  with  a 
"Woolf"  beam  engine,  at  Miinster,  which  was  made  at  the  shops  of  the 
Alsatian  Society  for  the  Construction  of  Machines. 

Second.    In  the  experiments  executed  in  1876,  under  the  auspices  of 

*This  chapter  comprises  translations  of  some  valuable  papers  contained  in  the 
"Bulletin  de  la  Societede  Mulhouse,"  a  journal  not  commonly  seen  in  the  United  States. 
The  author  has  endeavored  to  preserve  the  form  of  original  thought  as  nearly  as 
possible. 


THE  ALSA  77.1  .V  A'.V/'A/,'/  l//..\  7X  ETC.  189 


your  Mechanical  Committee  upon  a  horizontal  "Woolf "  engine  of  the  same 
make,  which  appeared  in  the  bulletin  for  July-August,  1877. 

Third.  In  those  executed  in  February,  1877,  by  the  Alsatian  Associa- 
tion of  Steam  Owners  upon  an  engine  at  Malmerspach  built  by  the  same 
company,  but  provided  with  a  variable  expansion  in  the  small  cylinder, 
controlled  by  the  governor,  and  provided  by  the  machine  company  of 
Bitsch  wilier -Thann. 

Fourth.  In  the  experiments  executed  at  St.  Remy  by  M.  Que'm,  and  at 
Rouen  by  the  Normandy  Association  of  Steam  Owners,  upon  two  "Woolf" 
beam  engines,  from  the  shops  of  Messrs.  Thomas  &  Powell,  of  Rouen. 

Having  discarded  the  experiments  of  which  the  verification  is  not 
exact  enough,  M.  Hallauer  determined  the  consumption  of  dry  saturated 
steam  per  hour,  and  for  each  absolute  horse-power,  per  indicated  horse- 
power per  hour,"  and  per  effective  horse -power  per  hour,  based  upon 
the  sum  of  the  calories*  brought  into  the  cylinder  by  the  steam  and 
water  leaving  the  boiler;  in  other  words,  substituting  for  the  entrained 
water  the  quantity  of  steam  which  could  furnish  to  the  cylinder  the  same 
number  of  calories  which  had  been  brought  by  that  water,  and  taking 
account  of  the  calories  left  in  the  jacket  by  the  steam  which  was  con- 
densed therein.  He  passes  then  to  the  analysis  of  each  experiment,  and 
determines  the  quantity  of  steam  and  water  contained  at  the  end  of  admis- 
sion and  at  the  end  of  stroke;  the  variations  of  the  internal  heat,  and  fin- 
ally of  the  cooling  in  the  condenser  Re.}  This  cooling  is  verified  by  two 
different  methods,  already  explained  many  times  by  Mr.  Hallauer  in  your 
bulletins. 

I  should  stop  a  moment  to  say  some  words  upon  the  verification  of  the 
experiments. 

M.  Hallauer's  very  elegant  manner  of  operating  has  already  been  given 
in  his  last  work.  However,  I  believe  it  is  not  useless  to  again  speak  of  it 
here  in  order  to  clearly  comprehend  its  importance. 

When  it  is  desired  to  render  an  account  of  the  quantity  of  steam  ex- 
pended during  a  given  time  by  an  engine,  the  water  fed  to  the  boiler  is 
measured.  This  quantity  of  water,  augmented  or  diminished  by  a  weight 
easily  calculated,  according  as  the  level  in  the  boiler  is  higher  or  lower  at 
the  end  of  the  experiment  than  it  was  at  the  beginning,  gives  the  quantity 
of  steam  used.  A  method  given  by  M.  G.  A.  Hirn,  and  many  times 
described  in  your  bulletins,  permits  the  determination  of  the  proportion 
of  water  entrained  with  this  vapor.  This  constitutes  the  direct  gauging, 
Avhich  is  verified  by  the  following  method: 

Knowing  the  weight  of  water  and  of  steam  leaving  the  boiler  and  the 
pressure  of  steam  therein,  it  is  easy  to  determine  the  number  of  calories 
brought  to  the  engine  per  stroke.  This  number  of  calories,  diminished 
by  the  external  cooling  and  the  heat  absorbed  by  the  work  done,  should 
be  equal  to  the  number  of  calories  absorbed  by  the  water  of  condensation, 

*A  calorie  is  §  X  2.204  =  3  9672  British  heat  units. 

tl  understand  by  lie  the  cooling  effect  of  the  condenser  upon  the  steam  in 
cylinders.— C.  A.  8. 


19O  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

a  quantity  obtained  by  gauging  the  water  leaving  the  condenser,  and 
measuring  the  initial  and  final  temperature.  The  manner  of  operation  has 
been  many  times  described.  The  difference  between  the  number  of 
calories  brought  to  the  engine  diminished  by  the  work  done  and  by  ex- 
ternal radiation,  and  that  of  the  calories  found  in  the  condenser  divided 
by  the  total  number  of  calories,  gives  the  per  cent,  of  error  which  has 
been  committed. 

A  word  also  concerning  the  term  "absolute  horse-power"  which  has 
not  always  been  easily  understood. 

The  fine  work  of  M.  Hirn  has  shown  the  enormous  iufluence  of  the 
sides  of  the  cylinder  upon  the  action  of  the  steam  therein  contained. 
When  two  engines  of  different  types  and  dimensions  are  compared,  or  the 
work  of  the  same  engine  under  varying  conditions,  it  is  the  influence  of 
the  internal  surfaces  which  should  be  determined  to  render  an  account  of 
the  manner  in  which  the  steam  is  utilized  in  each  experiment.  But  what- 
ever system  of  condenser  is  used,  the  influence  of  the  internal  surfaces 
can  only  vary  little;  but  on  the  other  hand,  the  vacuum  may  vary  within 
wide  limits,  and  consequently  the  indicated  work.  The  variable  vacuum, 
being  a  point  to  be  considered  if  one  compares  engines  by  their  indicated 
horse-power,  can  falsify  the  comparison.  We  are  then  forced  to  suppose 
that  engines,  presented  for  comparison,  are  furnished  with  an  ideal  con- 
denser keeping  a  perfect  vacuum  behind  the  piston,  and  to  compare  be- 
tween the  engines  an  account  of  the  work  furnished  with  this  perfect 
vacuum.  That  is  the  work  which  constitutes  the  absolute  work  of  the 
engine,  and  it  is  the  consumption  for  this  absolute  work  which  permits 
the  comparison  between  different  engines  or  of  different  conditions  of 
working.* 

It  is  well  understood,  for  the  rest,  that  from  the  practical  and 
industrial  point  of  view  the  better  the  condenser  the  better  the  re- 
sults; this  is  the  affair  of  the  builders,  but  can  have  little  influence 
upon  the  manner  in  which  the  steam  comports  itself  in  the  interior  of  the 
cylinder. 

The  absolute  work  is  then  the  term  to  be  employed  for  comparison  of 
two  engines  of  different  types,  or  working  under  different  conditions,  but 
the  effective  work  will  be  always  the  term  of  comparison  to  be  employed 
from  the  industrial  point  of  view. 

This  stated,  I  sum  up  in  the  following  table  the  results  of  the  verifica- 
tions and  analyses  of  M.  Hallauer,  and  with  him  I  arrive  at  the  deductions 
shown. 

The  experiments  executed  upon  the  engine  at  Minister,  in  which  the 
variation  of  work  is  obtained  by  throttling,  give  as  the  difference  of  con- 
sumption per  absolute  horse -power  per  hour  for  the  extremes  of  work 
3  per  cent.,  and  this  represents  the  effect  of  throttling. 

In  passing  to  the  effective  horse-power  per  hour,  the  economy  is  much 
more  considerable,  and  reaches  20  per  cent.,  which  shows  the  influence  of 


*In  English  it  is  usually  called  the  total,  or  forward  work.-  C.  A.  S. 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


191 


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192  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE, 

the  back  pressure  measured  with  the  work  done,  and  the  coefficient  of 
friction  which  augments  in  the  same  circumstances. 

M.  Hallauer  has  then  reached  the  conclusion  in  his  preceding  work 
that  the  most  simple  process  of  regulation  is  an  expansion  valve  regulated 
by  hand  and  the  governor  throttle,  the  control  by  hand  being  used  for  the 
larger  variations  and  the  throttle  for  maintaining  the  speed  uniform  in 
spite  of  the  minor  variations  of  work  which  may  occur  every  instant. 

The  author  also  explains  by  simple  considerations,  based  always  upon 
the  action  of  the  internal  surfaces,  some  apparent  anomalies  which  seem 
to  occur  in  the  experiments.  I  will  not  enter  into  these  details,  which 
would  compel  us  to  present  the  entire  work,  they  all  prove  that  the  practi- 
cal theory  pointed  out  by  M.  Him  and  applied  here  by  M.  Hallauer,  per- 
mits the  explanation  of  all  the  phenomena  which  take  place  in  the  interior 
of  cylinders.  After  having  studied  the  condensation  and  evaporation  in 
the  interior  of  the  small  and  large  cylinders,  and  noting  the  marked  differ- 
ences which  occur  from  an  expansion  more  or  less  prolonged  in  the  small 
cylinder,  M.  Hallauer  reaches  the  important  conclusions  which  follow, 
and  which  I  sum  up  under  a  slightly  different  form  from  that  which  he 
has  adopted. 

1.  Given  a  boiler  working  at  5.5  k.*  of  pressure,  for  instance,  and 
a  "Woolf "  engine  which  can  furnish  a  maximum  work  of  A  horse-power, 
there  is  a  possibility  of  obtaining,  industrially  at  least,  10  per  cent,  econ- 
omy by  cut-off  in  the  small  cylinder,  instead  of  throttling  down  the  steam 
at  the  times  when,  because  of  circumstances,  the  engine  has  to  supply 
only  the  half  of  A  horse-power;  this  economy  will  be  diminished  by  the 
measure  in  which  the  work  approaches  to  A  horse-power. 

2.  The  engine  working  nearly  to  its  maximum  capacity,  there  can 
be  produced  by  throttling  a  variation  of  force  of  10  per  cent,  without 
any  marked  change  in  the  economic  regime. 

We  see  at  once  the  importance  of  these  conclusions,  and  in  reality, 
there  are  few  "Woolf"  engines  working  at  full  power;  furthermore,  some 
builders  of  our  district,  when  they  furnish  an  engine,  declare  it  at  less 
than  one-half  the  power  that  it  really  is. 

Thus,  an  engine  sold  at  100- horse  power  can  ordinarily  furnish  200- 
horse  power  without  reaching  its  maximum.  This  mode  of  operation  has 
practical  advantages,  but  it  is  none  the  less  true  that  when  the  engine 
only  gives  100-horse  power,  thanks  to  the  throttling,  it  consumes  10  per 
cent,  more  than  it  would  have  consumed  if  the  work  of  100-horse  power 
had  been  obtained  by  admitting  full  pressure  and  cutting  off  in  the  small 
cylinder. 

I  do  not  agree  with  M.  Hallauer  when  he  recommends  a  cut-off  vari- 
able by  hand.  I  believe  that  from  the  practical  point  of  view  a  governor 
cut-off  works  better,  for  it  disposes  of  the  neglect  of  the  engineer,  who 
may  not  be  able  very  well  to  give  the  desired  cut-off  the  moment  that  it 
should  be  applied.  We  have  nearly  always  observed  that  an  automatic 
expansion  procures  a  more  regular  speed  than  a  governor  throttle. 

*14.223  pounds  per  square  inch  =  1  k.  per  square  centimetre. 


THE  ALSATIAN  EXPERIMENTS,  ETC.  193 


SECOND   PAET. — INFLUENCE  OF  CUT-OFF  IN  SINGLE   CYLINDER  ENGINES. 

M.  Hallauer  proceeds  for  these  engines  as  he  did  for  the  compound 
engine.  He  first  verifies  the  experiments  upon  which  he  rests;  then  he 
analyzes  them. 

The  documents  which  have  served  for  this  study  resulted  from  the 
following  experiments: 

First.  Those  executed  under  the  auspices  of  your  mechanical  com- 
mittee in  April  and  May,  1878,  upon  a  Corliss  engine,  constructed  by 
Messrs.  Berger,  Andre  &  Co.,  of  Thann. 

Second.  Those  undertaken  in  1873  and  1875  by  Messrs.  Hallauer,  Gros  • 
seteste  and  Dwelshauvers-Dery,  under  the  inspiration  of  M.  G.  A.  Hirn, 
and  executed  upon  an  engine  deprived  of  its  jacket,  and  working  with 
superheated  and  with  saturated  steam.  We  group  the  results  of  the  veri- 
fications and  analyses  in  the  table  which  follows. 

The  examinations  of  these  results  show: 

First.  That  for  the  Corliss  engine,  with  steam  jacket,  there  is  a  theo- 
retical economy  per  absolute  horse-power  of  1^  per  cent,  when  the  cut- 
off is  changed  from  £  to  Jj,  but  that  industrially,  this  economy  disappears 
and  changes  sign,  and  there  is  a  practical  gain  per  effective  horse -power 
of  4^  per  cent,  by  working  at  J  cut-off  in  place  of  -ff. 

Second.  That  for  the  engine,  without  jacket  and  without  superheat- 
ing, the  economy  furnished  by  the  cut-off  is  much  more  considerable  than 
the  Hirn  engine  working  with  saturated  steam,  and  that  there  is  a  theo- 
retic gain  of  7.4  per  cent,  by  changes  to  cut-off  \  from  £,  and  that,  indus- 
trially, this  economy  remains  at  4  cent. 

Third.  In  taking  account  of  the  difference  of  superheating,  the  ex- 
periments I.  and  II.  (106°  C.  and  231°  C.),  establish  the  fact  that  the  in- 
fluence of  the  cut-off  in  the  unjacketed  engine,  with  superheated  steam, 
remains  as  it  did  with  saturated  steam. 

Experiment  III.,  with  superheated  steam,  shows  still  more  the  great 
economy  of  the  cut-off  in  these  circumstances,  where  one  passes  certain 
limits,  for  between  admissions  of  £  and  |  there  is  15  per  cent,  economy, 
which  would  have  been  more  considerable  if,  in  experiment  I.,  we  had 
worked  with  the  same  superheating  as  in  experiment  III. 

Fourth.  In  the  Hirn  engine  the  experiments  with  saturated  steanj  give 
at  the  end  of  the  stroke  the  same  weight  of  water,  0.0940  k.*  and  0.0927  k., 
and  the  refrigeration  is  also  the  same,  37.53°  C.  and  37.02°  C.,  while  with- 
out any  jacket  the  same  weights  of  water  gave  the  same  values  of  Re.  For 
the  Corliss  engine,  on  the  contrary,  the  weights  of  water  differ  at  the  end 
of  the  stroke,  0.0298  k.  and  0.0398  k.,  and  the  same  refrigeration,  11.21°  C. 
and  11.15°  C.,  results  showing  the  steam  jacket.  For  experiments  II.  and 
III.,  with  superheating,  the  weights  of  water  at  the  end  of  the  stroke  are 
0.0367  k.  and  0.0373  k.,  and  the  refrigerations  16.61°  C.  and  20.34°  C.,  a  dif- 
ference which  should  be  attributed  to  superheating,  for  in  the  same  con- 

*i  k.  =  2.204  pounds. 


194 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


O  ** 

X  X 


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i-l         iHrHOSO>OCOt- 

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expansion  

error  committed  
actual  horse-power  per  hour  
indicated  horse-power  per  hour, 
effective  horse-power  per  hour.  . 
condensed  in  jacket  
water  at  end  of  admission  
expansion  
radiated  to  the  condenser  by  t 

cent,  of  heat  received  

r""«^  ^ h o 

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British  I. 
Pounds  w 


THE  ALSA TIAN  EXPERIMENTS,  ETC.  195 


ditions  saturated  steam  rejects  heat  in  the  condenser  according  to  the 
weight  of  water  evaporated  at  the  end  of  the  stroke.  This  shows  that 
superheating  acts  in  a  different  manner  from  jacketing. 

Analyzing  the  variations  of  internal  heat  in  the  various  experiments 
before  us,  and  the  values  of  the  refrigeration  in  the  condenser  which  re- 
sult from  differences  of  cut-off,  according  as  they  work  with  or  without  a 
jacket,  and  with  or  without  superheating,  M.  Hallauer  comes  to  the  same 
conclusion  as  to  the  different  modes  of  action  of  the  jacket  and  super- 
heater. The  jacket  acts  more  energetically  than  the  superheater,  and  sim- 
ilarly during  the  period  of  expansion,  but  becomes  disadvantageous  dur- 
ing that  of  condensation,  for  then  it  furnishes  heat  to  the  water  which 
lines  the  internal  surface  of  the  cylinder,  and  augments  that  rejected 
into  the  condenser,  which  is  not  the  case  with  superheating;  this  renders 
the  latter  more  economical  in  most  cases.  Examining,  then,  the  theoretic 
economy,  and  comparing  the  consumption  per  absolute  horse-power  per 
hour,  the  industrial  economy  and  the  amounts  per  effective  horse-power 
per  hour,  the  author  agrees  with  M.  Zeuner  that  large  expansions  are 
economical  from  a  theoretical  point  of  view,  and  with  M.  Hirn  that  the 
reverse  is  the  case  from  an  industrial  standpoint. 

Thus  the  conclusions  of  these  two  savants,  which  had  the  air  of  con- 
tradiction, are  found  to  be  in  accord,  taking  account  of  the  different  con- 
siderations which  guided  them;  the  one,  M.  Zeuner,  having  made  a  gen- 
eral study  of  steam  engines  based  upon  conditions  non- realizable  (non- 
conducting internal  surfaces  of  the  cylinder);  the  other,  M.  Hirn,  on  the 
contrary,  having  studied  them  from  the  industrial  basis,  and  taking 
account  of  the  action  of  the  internal  surfaces  and  the  work  done  in 
friction. 

THIRD   PAKT. — COMPARISON  OF  THE  DIFFERENT  TYPES   OF  ENGINES 

STUDIED. 

The  close  of  M.  Hallauer's  work  includes  the  comparison  of  compound 
and  simple  engines;  still  taking  the  analysis  of  the  experiments  which 
served  for  the  two  first  parts  of  the  work,  he  restates  what  he  understands 
by  absolute,  indicated,  and  effective  horse-power. 

The  absolute  work  is  the  work  which  would  have  been  given  by  the 
engine  with  an  ideal  condenser,  making  a  perfect  vacuum  behind  the  pis- 
ton,— the  theoretical  work.* 

The  indicated  work  is  that  furnished  by  the  steam  upon  the  pistons;  it 
includes  the  influence  of  back  pressure; — it  is  the  work  which  the  dia- 
grams traced  by  the  indicator  enables  us  to  calculate. 

The  effective  work  is  then  the  work  industrially  disposable;  it  takes 
account  of  the  back  pressure  and  the  friction  of  the  various  parts  of  the 
engine  itself. 

That  stated,  we  have  two  of  the  verified  experiments:  one  executed 
upon  the  Corliss  engine,  cutting  off  at  £,  the  other  at  the  Malmerspach 

*The  forward  work. 


196  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

engine,  cutting  off  at  ^  in  which  the  figures  approach  each  other  as 
closely  as  possible. 


Corliss.      Woolf. 

per  cent,  per  cent. 

Water  contained  at  the  end  of 

admission      

OK  3_            OQ  7_ 

expansion 

18  5         II-9- 

Difference  of  initial  and  final 

heat 

Rejected  in  condenser.  .  . 

The  comparison  of  these  two  experiments  brings  us  to  very  interest- 
ing conclusions. 

A  phenomenon  to  be  first  noted  for  the  "Woolf"  engine  destroys  a  false 
idea  held  hitherto:  that  for  the  double -cylinder  engine  a  portion  of  the 
force  is  withdrawn  from  the  cooling  influence  of  the  condenser. 

In  reality,  in  the  small  cylinder  the  expansion  from  half  stroke  gave 
place  to  an  evaporation  of  10.6  per  cent,  of  the  weight  of  water  contained 
at  the  end  of  admission,  and  the  internal  heat  increased  much  more  rap- 
idly than  in  the  Corliss  engine.  Then  the  mixture  of  steam  and  water 
passed  to  the  large  cylinder  with  13.1  per  cent,  of  water,  and  in  place  of 
the  evaporation  continuing  in  this  cylinder  there  was,  on  the  contrary, 
condensation,  in  spite  of  the  jacket,  till  at  the  end  of  the  stroke  4.8  per 
cent,  more  water  was  deposited  than  at  the  end  of  the  stroke  in  the  small 
cylinder.  This  shows  that  the  great  condensation  at  the  moment  of 
entrance  into  the  large  cylinder  is  strong  enough,  in  spite  of  the  jacket; 
that  all  the  steam  condensed  in  the  large  cylinder,  and  that  which  has 
come  from  the  small  cylinder,  cannot  be  evaporated. 

In  the  Corliss  engine,  on  the  other  hand,  there  is  a  continuous  evapo- 
ration till  the  end  of  the  expansion.  We  see  that  the  influence  of  the 
large  cylinder  in  the  case  of  expansion,  commenced  in  the  small  cylinder, 
does  not  always  tend  to  lessen  the  rejected  heat,  but,  on  the  contrary,  may 
sometimes  augment  it,  which  is  the  reverse  of  that  which  has  been  hith- 
erto admitted. 

The  consumption  of  dry  saturated  steam  per  absolute  horse -power  per 
hour  gives  the  theoretic  economy  realized  by  the  one  or  the  other  motor. 
If  we  compare  the  consumption  of  the  Corliss  with  that  which  it  would 
have  had  with  an  expansion  of  13,  which  is  that  of  the  "Woolf"  engine, 
for  the  experiment  with  which  we  compare,  we  find  that  the  theoretic 
economy  is  4  per  cent,  in  favor  of  the  "Woolf"  engine;  but  the  influence 
of  the  back  pressure,  and  still  more  that  of  the  friction,  reduces  this 
economy  when  we  pass  into  the  industrial  domain.  It  then  changes  sign, 
and  we  find  that  the  practical  economy  becomes  8.7  per  cent,  in  favor 
of  the  Corliss. 

Comparing,  then,  the  horizontal  "Woolf"  engine  with  the  Corliss,  and 
taking  account  of  the  lack  of  compression  in  the  former,  M.  Hallauer  finds 


THE  ALSATIAN  EXPERIMENTS.  ETC.  197 

again  a  theoretic  economy  of  4  per  cent,  for  the  "Woolf"  engine,  but  that 
economy  also  disappears  in  practice,  and  the  Corliss  becomes  industrially 
superior  by  9.05  per  cent,  to  the  horizontal  compound.  Meanwhile,  con- 
sidering the  construction  of  this  latter,  the  difference  falls  to  2  per  cent., 
and  then  the  horizontal  "Woolf"  engine  consumes  only  8.8  k.  of  dry 
saturated  steam  per  effective  horse-power  per  hour,  which  is  the  smallest 
consumption  at  which  we  can  arrive  by  a  careful  construction  of  condenser, 
and  a  very  strong  compression.  In  closing,  M.  Hallauer  sums  up  in  a  table 
the  consumption  of  steam  per  hour  per  horse-power,  absolute,  indicated 
and  effective,  adding  the  consumption  per  effective  horse-power  per  hour 
of  coal,  on  the  basis  of  an  evaporation  of  8. 

The  table  shows  that  the  various  types  of  double  cylinder  engines  con- 
sume from  9.1  to  9.5  k.  of  steam  per  effective  horse-power  per  hour;  the 
Corliss,  with  cut-off  £,  only  uses  8.6  k.,  while  the  Hirn  engine,  with  super- 
heated steam,  and  f  cut-off,  only  uses  8k.,  or  17.6  pounds. 

To  sum  up:  The  work  of  M.  Hallauer,  which  is  one  of  those  laborious 
and  conscientious  studies  to  which  he  has  so  long  accustomed  our  society, 
is  above  all  very  remarkable  in  its  conclusions  an/1  tends  once  more  to 
prove  the  impossibility  of  stating  anything  with  precision  concerning 
steam-engines,  if  one  does  not  rest  on  verified  experiments  of  existing 
engines. 

We  have  been  compelled  in  this  summary  to  leave  untouched  many 
interesting  things,  aiming  mainly  to  unite  the  divers  conclusions  of  M. 
Hallauer;  but  all  parties  concerned  in  steam-engines  will  certainly  find  in 
his  work  exceedingly  useful  material  to  serve  them  in  many  circumstances. 
We  are  cognizant  of  owing  many  thanks  to  M.  Hallauer  for  all  these  inves- 
tigations which  demand  so  much  time,  patience,  and  reflection,  all  of 
which  he  has  not  been  sparing  in  this  his  last  memoir;  you  know,  for  the 
rest,  what  he  is  accustomed  to  do,  by  the  numerous  works  which  he  has 
already  presented  to  our  society,  and  of  which  this  last  gives  the  most 
interesting  practical  conclusions. 

EXPERIMENTS  WITH  A  STEAM  ENGINE. — A  MEMOIR,  PRESENTED  BY  M.  O. 
HALLAUER,  KELATING  TO  THE  EXPERIMENTS  DIRECTED  BY  M.  G.  A. 
HIRN,  EXECUTED  BY  M.  M.  DWELSHAUVERS-DERY,  W.  GROSSETESTE 
AND  O.  HALLAUER. 

In  his  recent  work  on  Thermodynamics  M.  Hirn  describes  the  remark- 
able progress  that  the  judicious  employment  of  the  principles  of  this  new 
science  has  brought  about  in  the  study  of  heat  engines,  at  the  same 
time  that  it  shows  that  various  edifying  theories  were  far  from  the  reality; 
finally  it  proves  with  evidence  the  impossibility  of  general  theories. 

If  we  take  up  this  question  so  fully  treated  by  him;  if  we  analyze  one 
after  the  other  the  experiments  made  under  his  direction;  it  is  to  the  sin- 
gle end,  as  he  himself  has  well  said,  "of  shunning  the  numerous  blunders" 
of  practical  men  who  have  wished  to  pursue  such  studies;  and  it  will  also 
be  seen  how  we  have  obtained  an  experimental  solution  of  many  important 


198  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

problems  not  yet  studied,  so  that  we  can  encourage  engineers  on  a  track 
so  fruitful  of  results,  for  we  are  certain  that  researches  of  this  nature  lead 
to  one  useful  end,  the  reduction  of  fuel.  But  in  order  that  this  memoir 
may  serve  as  a  guide  in  new  work,  it  is  essential  to  give  here  the  method  of 
experiment  so  happily  inaugurated  by  M.  Him  and  so  often  described  by 
him. 

METHODS    OF   EXPERIMENTS. — BRIEF   DESCRIPTION   OF   THE  ENGINE. 

The  engine  with  which  we  worked  was  a  beam  engine,  with  vertical  un- 
jacketed  cylinder  and  four  valves,  two  for  admission  and  two  for  exhaust. 
A  differential  movement  of  the  two  cams  which  worked  the  admission 
permitted  us  to  vary  the  angle  at  will,  and,  consequently,  at  various  de- 
grees following  the  needs  of  the  experiments.  The  steam  brought  to  the 
cylinder  immediately  on  leaving  the  boiler  passed  through  many  tubes, 
of  cast-iron,  placed  behind  the  boiler  in  a  special  chamber  where  the  sim- 
ple movement  of  two  registers  brought  in  the  hot  gas.  The  steam  carried 
with  it  a  degree  of  superheating  which  ranged  from  195°  C.  to  231°  C.,  while 
it  could  be  brought  to  the  engine  in  the  state  it  left  the  boiler  by  chang- 
ing the  registers  to  give  direct  passage  to  the  pipe.  The  consequence  of 
this  analysis  will  lead  us  to  see  that  M.  Him  in  constructing  the  most 
practical  engine  actually  known,  has  also  made  a  veritable  instrument  of 
precision  for  researches  in  experimental  physics.  The  dispositions,  as  sim- 
ple, as  ingenious,  which  he  adopted  to  assure  the  exactness  of  the  opera- 
tions have  served  in  most  cases. 

Observations  Taken. — These  are  grouped  into  three  distinct  series:  the 
measurement  of  the  water  consumed  and  rejected  from  the  condenser, 
those  of  temperatures  and  the  work. 

1.  The  quantity  of  steam  that  the  engine  consumed  was  obtained  by 
direct  measurement;  the  easiest  made  the  water  for  the  feed  pump 
flow  through  a  reservoir  of  constant  known  volume,  alternately  filled  and 
emptied.  If  the  water  level  in  the  boilers  is  noted  evening  and  morning, 
and  account  taken  of  this  difference  of  level,  the  only  precaution  neces- 
sary is  to  ascertain  by  hydraulic  pressure  that  no  leaks  exist  in  the  boiler, 
superheater  and  pipes.  The  total  weight  of  feed  water  passing  the  gauge 
tank  divided  by  the  number  of  strokes,  B,  during  the  day,  gives  us  the 
water  consumed  per  stroke,  M. 

That  rejected  by  the  air  pump  is  also  gauged,  but  differently.  At  the 
outlet  a  pit  of  masonry  is  arranged;  its  capacity  at  different  heights  was 
determined  by  putting  in  known  weights  of  water,  and  at  the  bottom  of 
this  plate  a  copper  plate  was  placed,  pierced  with  a  circular  orifice  0.06  m. 
diameter,  out  of  which  continually  flows,  under  a  head  of  from  0.6  m.  to 
0.8  m.,  the  water  brought  from  the  condenser.  The  discharge  of  this 
orifice  is  found  experimentally  by  closing  it  tightly  by  a  stopper,  filling 
to  a  known  height  and  noting  the  time  it  takes  to  lower  each  0.1  m. 

Let  S  be  the  horizontal  section  of  the  pit,  s  the  area  of  discharge,  and 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


199 


n  an  unknown  coefficient  of  contraction,  h  the  head  above  the  centre  of 
the  orifice,  and  t  the  time.    We  then  have: 

—  Sdh  =  nadt  Vfyh 
2  &  (VHt  —  VHJ  =  naTV2g 


This  gives  at  once  na  V2g  when  the  time  T  is  noted,  while  the  level 
falls  from  H0  to  H^ 

The  volume  of  water,  or  the  weight  rather,  running  out  under  head 
H ,  is  II  =  (na  Vfy)  VH. 

During  the  days  of  experiments  we  noted  every  fifteen  ininutes  the 
heads  h0,  hlt  h».  .  .  these  varied  little  and 

— - — - — '  ;  or,  more  simply  even 


whence  II  =  (ns  VW  v/7im  ±  8  (hl~ 


&!  and  h*  are  initial  and  final  heads  of  an  experiment  whose  duration  was 
T.    If  in  this  time  the  engine  made  B  strokes  the  weight  of  water  rejected 


II  T 

per  stroke  was  J/0  =    -—  . 
B 


The  injection  per  stroke  was  II—  M. 


We  give  in  tabular  form  the  values  obtained  in  eight  experiments, 
each  consuming  an  entire  day: 


TABLE  I. 


DATE. 

Superheat'ng. 

Expansion. 

Weight  of 
Steam 
Consumed. 

Injection 
Water. 

Nov.  18,  1873   

231°    C 

4 

0  3065 

9.3500 

Nov   28,  1873 

none 

4 

0  3732 

9  29175 

Aug.  26,  1875 

215° 

5 

0  2651 

8  7291 

Aug.  27,     "     

223° 

2  throttled. 

0.  2822 

8  5983 

Sept.  7,    " 

195° 

7 

0  2240 

8  7384 

Sept.  8,    "    

none 

7 

0.2634 

8  .  9132 

Sept.29,   "    
Oct.  28,     "    

220° 
220° 

2  throttled, 
non-condens  - 

0.2265 
0  2715 

5.9810 

ing. 

2.  Temperatures. — Part  of  these  are  noted  directly,  but  with  different 
instruments.  To  arrive  at  the  superheating  a  good  thermometer  is  simply 
placed  in  mercury  in  a  copper  pocket  open  at  one  end  and  closed  at 
the  other  and  let  into  the  steam  pipe ;  this  measurement  is  easy  to 
obtain. 

The  rise  of  temperature  of  the  injection  water  in  the  condenser  neces- 
sitates a  more  careful  measurement — a  special  thermometer  known 
already  to  the  readers  of  our  Bulletins,  the  differential  air  thermometer. 


200 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


The  practical  arrangements  that  M.  Him  brought  about  this  instrument 
permitted  the  obtaining  to  the  fiftieth  of  a  degree  the  increase  in  tempera- 
ture. We  will  only  indicate  the  method  of  procedure  with  its  use  without 
entering  upon  any  detailed  account  of  the  construction  of  the  instrument. 

Two  thermal  reservoirs  filled  with  perfectly  dry  air,  connected  to  indi- 
cating tubes  by  capillary  copper  tubes,  are  both  plunged  into  the  cold 
injection  water  and  put,  by  opening  three-way  valves  with  which  they 
are  fitted,  into  communication  with  the  external  air.  The  temperature  of 
the  cold  water  is  also  noted  with  a  good  mercurial  thermometer  reading 
to  the  tenth  of  a  degree,  also  the  divisions  where  the  indicating  liquid  in 
the  pressure  tubes  stops;  finally,  the  height  of  the  barometer.  A  turn  of 
the  three-way  valve  closes  the  connection  to  the  external  air,  while  it 
leaves  open  that  between  the  reservoirs  and  indicating  tubes  of  the  appa- 
ratus. Placing  then  one  reservoir  in  the  cold  water  brought  to  the  injec- 
tion, the  other  in  the  warm  water  rejected,  we  note  every  quarter  of  an 
hour  the  heights  of  the  liquid.  The  averages  for  an  entire  experimental 
day  are  transformed  to  degree,  centigrade,  and  give  by  their  difference  the 
rise  in  temperature  of  the  water  during  that  day.  The  formula  for  the 
air  thermometer  is  as  follows  : 

Let  .B=height  of  barometer  at  start. 

i= temperature  of  cold  water  at  start. 

5/=mean  height  of  barometer  during  the  day. 

£= temperature  sought. 

y— Coefficient  of  dilatation  of  the  reservoir,  usually  copper. 

a=that  of  the  air. 

p_     «     tt    tt  indicating  liquid. 

a = temperature        "  " 

V=  volume  of  reservoir. 

s/i=      "       "  liquid  moved  in  tube. 

Then: 

/      V      \  /I  +  /A  /I  +  a 


13.596  Bf 


,o  r 

=  13- 


+ 


By  taking  large  reservoirs,  — — — -  =  1  nearly. 

Practically,  when  we  only  have  in  view  industrial  results,  the  employ- 
ment of  a  good  mercurial  thermometer  reading  to  tenths  of  a  degree  con- 


TABLE  II. 


Nov.  18. 

Nov.  28. 

Aug.  26. 

Aug.  27. 

Sept.  7. 

Sept.  8.  \  Sept.  29. 

Temperature  of  in- 
jection   

31.3 

33.65 

33.09 

35.26 

30.42 

32.25            37.81 

Temperature  of  re- 
jection .  .  . 

12.6 

11.83 

16.50 

16.50 

16.37 

16.50            15.85 

j 

Difference  

18.7 

21.82 

16.59 

18.76 

14.05 

15.75     i       21.96 

THE  ALSATIAN  EXPERIMENTS,  ETC. 


2O1 


duces  to  results  sufficiently  close,  but  there  are  times  when  their  use  is  far 
from  being  as  convenient  as  that  of  the  air  thermometer. 

The  other  temperatures  corresponding  to  the  steam  pressures  are 
taken  from  the  tables  of  Eegnault.  They  are  thus  obtained  indirectly,  and 
are  experimental;  for  these,  tables  of  pressure  and  temperature  are 
deduced  from  observation. 

The  values  which  serve  us  were  obtained  by  a  generator  and  free -air 
manometer,  and  in  the  interior  of  the  cylinder  by  measurement  upon  the 
diagrams  of  work,  which  gives,  as  all  know,  the  curve  of  pressure  for  each 
point  in  the  stroke  of  the  piston. 

TABLE  III 


00 

1 

1 

£ 

150.00 
124.00 
94.40 
58.25 

I 

06           8' 

43 

a 

O 

Temperature  in  boiler. 

150.15  148.20151.00 
144.96  140.78148.74 
97.24    98.24    92.05 
73.49J  73.42    58.86 

| 
150.77150.77  151.20146.20 
142.00  141.30  115.80  137.49 
85.00    84.33)  87.36101.89 
58.44    61.15!  57.11  

Temperature  at  cut-off  

Temperature  at  end  stroke  

Temperature  during  exhaust  

3.  Measurement  of  the  Work. — This  requires  the  most  minute  care  and 
was  effected  by  the  aid  of  two  sets  of  apparatus,  the  one  checking  the 
other — the  indicator  of  Watt  and  the  pandynamometer  of  flexion  of  Hirn 
— this  latter,  above  all,  installed  in  very  favorable  conditions,  has  fur- 
nished us  values  most  remarkable  for  their  exactness.  We  have  then, 
based  upon  the  results  which  it  gave,  analyses  in  which  the  de- 
termination of  the  various  works,  with  full  pressure,  with  expansion, 
the  total  forward  work,  plays  an  important  part ;  also  the  measurement  of 
pressures  at  the  points  of  the  stroke  where  we  wish  to  study  the  thermic 
conditions  of  the  steam  and  the  transformations  to  which  it  is  sub- 
mitted. 

It  is  owing  to  the  happy  idea  of  utilizing  as  a  spring  the  beam  of  the 
engine  that  M.  Hirn  arrived  at  the  construction  of  the  instrument  which 
he  has  already  described  in  our  Bulletins.  This  apparatus  draws  at  each 
instant  the  deflection  of  the  beam,  and  gives  a  curve,  of  which  the 
abscissas  are  proportioned  to  the  stroke  and  the  ordinates  to  the 
pressures. 

The  study  of  the  diagrams  drawn  by  these  instruments  is  nearly  the 
same.  The  indicator,  then,  is  less  exact  for  engines  with  a  single  cylinder, 
but  it  has  been  long  used,  not  as  an  instrument  of  analysis,  but  as  a  means 
of  measuring  work,  while  we  only  insist  on  the  curves  traced  by  the 
pan  dynamometer. 

With  this  latter  the  scale  of  abscissas  is  obtained  by  direct  measure- 
ment upon  the  movable  plate  and  for  equal  parts  of  the  stroke;  that  of  the 
ordinates  by  a  direct  comparison;  the  engine  is  brought  to  one  of  its  dead 
points,  the  steam  turned  into  the  cylinder  at  a  known  pressure,  the  force 


2O2 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE, 


exerted  on  the  piston  is  transmitted  to  the  beam  which  deflects  an  amount 
measured  by  the  pencil  of  the  apparatus.  Then  to  check  in  the  reverse 
direction,  the  crank  is  put  on  the  other  dead  point  and  the  operation  re- 
peated. M.  Hirn  has  established,  every  twentieth  of  the  stroke,  the  load, 
in  kilogrammes,  needed  to  bend  the  beam  such  an  amount  that  the  pencil 
of  the  dynamometer  shall  describe  an  arc  of  a  circle  of  one  metre  in  de- 
velopment; it  is  the  unit  of  measure  at  each  corresponding  twentieth  of 
the  stroke. 

All  the  curves  drawn  have  been  carefully  measured;  the  mean  ordinates 
transformed  into  kilogrammes  upon  the  piston  are  set  off  on  the  corres- 
ponding lines,  10  millimetres  for  1,000  kilogrammes.  At  the  same  time  we 
trace  below  the  axis,  to  the  same  scale,  the  values  of  the  vacuum  given  by 
the  indicator  alone,  joining  the  extremities  by  a  curve,  drawn  full  for  the 
pressure,  and  dotted  for  the  vacuum.  Between  these  curves  we  have  the 
pressure  carried  at  each  moment  by  the  piston.  If  the  absolute  vacuum 
could  have  been  reached  on  one  side,  while  the  steam  acted  on  the  other, 
nothing  is  more  easy  than  to  establish  the  pressure  per  square  metre;  the 
load  divided  by  the  piston  area  gives  it. 

This  known,  the  tables  of  Regnault,  or  the  formula  of  Roche,  fix  the 
corresponding  temperature,  and  we  can  calculate  then : 

y  the  densities, 

A  the  total  heat  of  evaporation, 

ZJthe  internal  heat,  etc., 

of  the  steam  at  points  of  the  stroke  which  interest  us,  without  which 
values  any  analysis  is  impossible. 

Finally,  the  planimeter,  by  a  measure  of  the  area,  gives  us  the  different 
kinds  of  work,  the  forward  work  at  full  pressure,  the  total  forward  work, 
the  total  indicated  work,  and  the  effective  work,  or  the  difference  between 
the  indicated  work  and  that  absorbed  by  the  friction  of  the  parts  of  the 
engine. 

TABLE  IV. 


Nov.  18. 

Nov.  28. 

Aug.  26. 

Aug.  27. 

Sept.  7. 

Sept.  8. 

Sept.  29. 

Oct.  28. 

Revolutions  per 
minute  

30.1736 

30.5494 

29  .969 

30  306 

29.98 

30  41 

30  13 

30.00 

T.  H.  P.  in.  ch.d. 
v.  ot  75  kgms.  in 
forward  work.. 

144.36 

136.46 

135.77 

125.17 

113.08 

107.81 

99.53 

78.30 

Checking  the  Consumption. — Thanks  to  the  data  taken,  we  can  estab- 
lish an  equality  in  the  heat  brought  to  the  engine  and  that  used  in  work 
and  rejected  from  the  condenser,  so  that  we  can  make  a  first  verification 
showing  with  what  approximation  we  have  noted  the  consumption  of 
steam. 

The  first  fundamental  proposition  of  thermodynamics  experimentally 
established  is  that,  heat  acting  upon  a  body  gives  place  to  mechanical 
work  and  a  quantity  of  heat  proportioned  to  the  work  disappears;  the 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


2O3 


relation  between  work  produced  and  heat  disappearing  is  constant  and 
depends  in  no  way  upon  the  body  by  which  it  acts.  We  should  then  have 
between  the  heat  brought  to  the  engine  and  that  found  in  the  injection 
water  a  difference,  a  decrease  proportioned  to  the  external  work  done, 
or  the  forward  work.  The  value  of  this  decrease  is  no  other  than  the  quo- 
tient of  the  number  of  kilogrammetres  furnished  by  the  engine  per  stroke, 
divided  by  425  kilogrammetres,  the  equivalent  of  a  calorie  transformed 
into  work. 

Take  for  example  the  experiment  of  August  26,  1875,  with  steam  at 
21 5°  C.  The  mean  consumption  per  stroke  for  this  day  is  0.2651  k.  Taking 
the  boiler  pressure,  49,938  kgs.  per  sq.  metre,  a  temperature  of  151°  C.,  it 
takes  from  the  boiler  0.2651  k.  x  h  =  0.2651  k.  (606.5  +  0.305  x  151);  but 
before  reaching  the  cylinder  it  traverses  the  superheater,  which  raises  its 
temperature  to  215°  C.,  and  furnishes  to  the  fluid  0.5  x  0.2651  (215—151) 
more.  The  specific  heat  of  steam  being  0.5,  finally,  when  this  fluid  leaves 
the  condenser,  it  takes  with  it  0.2651  /  =  0.2651  x  33.09,  which  it  is  necessary 
to  take  away  from  the  amount  brought,  and  we  have  for  the  heat  available 
in  the  cylinder. 

Qa  =  0.2651  k.  (606.5  +  .305  x  15*1°  +  0.5  (215°  —  151°)  —  33.09.)  = 

172.79  c. 

The  cold  water  of  injection,  measured  as  above  is,  8.7291  k.;  it  receives 
from  the  steam  which  it  condenses  Ql  =  8.7291  k.  (f—i)  =  8.7291  k.  +  16.59 
=  144.82  c. 

There  has  disappeared  in  the  interval: 

172.79  —  144.82  =  27.97  c. 

But  we  have  used  externally  135.77  ch.,  say  10,193  kgms.  per  stroke,  which 
has  absorbed  23.99c.  The  external  radiation  of  the  cylinder  has  been  2.5c., 
total  of  26.49c.,  a  difference  of  1.48c.,  say  of  0.8  per  cent,  of  172.79c.  brought 
to  the  cylinder.  This  is  the  error  and  check  upon  the  consumption,  as  the 
distinction  between  the  observations  is  clearly  defined. 

TABLE  V. 


Nov.  18. 

NOV.  28. 

Aug.  26. 

Aug.  27. 

Sept.  7. 

Sept.  8. 

Sept.  29. 

Oct.  28. 

Heat  brought. 

202.72 

228.80 

172.79 

184.41 

144.34 

161.51 

147.05 

g 

Heat  in  work 

p 

and  radiated 

27.82 

26  15 

26.49 

24.36 

22.47 

21.27 

19.99 

Is 

Difference.. 

174.90 

202.65 

146.30 

160.05 

121.87 

140.24 

127.06 

2LP 

Heat  rejected 

174.84 

202.75 

144.82 

161.30 

122.77 

140.38 

131.34 

£  ' 

Error  

+0.06 

—0.10 

+  1.48 

—1.25 

—0.90 

0.14 

—4.28 

We  see  that  all  the  errors  but  that  of  the  29th  September  are  less  than 
1  per  cent.  The  latter  has  an  error,  of  which  we  cannot  discover  the  cause, 
which  does  not  exceed  3  per  cent. 

Verification  of  the  Work. — To  be  more  correct,  we  should  describe  the 
verification  of  the  indicator,  for  the  simple  inspection  of  the  curves  drawn 


2O4 


STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


by  the  aid  of  the  pandynamometer  renders  evident  the  superiority  of  this 
method  of  valuing  the  force.  And  we  may  add  that  many  successive  ex- 
periments always  led  M.  Hirn  to  the  same  results  and  the  same  coefficients 
for  the  scales  of  pressures.  On  the  other  hand  the  sufficiently  large  curves 
permit  us  to  obtain,  with  much  exactness,  not  only  the  pressures  but  also 
the  fractions  of  the  stroke  and  consequently  the  volumes  affected  by  the 
cut-off;  also,  by  taking  these  curves  and  comparing  them  with  the  indi- 
cator diagrams  taken  under  the  same  conditions,  we  form  the  following 
table: 


TABLE  VI. 


Aug.  26. 

Aug.  27. 

Sept.  7. 

Sept.  8. 

Sept.  29 

Oct.28. 

Pressure  in  metres  of  mercury  : 
Pandynamometer  

3  013 

2  790 

2.91 

2  91 

2  93 

2.475 

Indicator 

3  007 

2  806 

2  80 

2  91 

2  94 

2  475 

Full  pressure  forward  work,  kgm.  : 
Pandynamometer 

4  175 

6  285 

3  365 

3  235 

4  880 

4  800 

Indicator  

3.990 

6  148 

3  120 

3  135 

4  930 

4  702 

Difference  per  cent  

+4  43 

+  2  17 

+7  25 

+  3.09 

—1.00 

+  2  08 

Forward  work  of  expansion  : 
Pandynamometer 

6  700 

3  930 

6  185 

5  965 

3  120 

6  575 

Indicator  

6  621 

3  875 

5  885 

5  985 

3  192 

6  697 

Difference  per  cent  

+  1.19 

+  1.39 

+4  85 

—0.33 

—  2  30 

—1.85 

Total  forward  work  : 
Pandynamometer 

10  875 

10  215 

9  550 

9  200 

8  000 

11  375 

Indicator    .... 

10  611 

10  023 

9  006 

9  120 

8  122 

11  399 

DilTerence  per  cent    .  .  . 

+  2.42 

+1  91 

+  5  69 

+  0  86 

—1.52 

—0.21 

Indicated  work  : 
Pandynamometer 

9  870 

9  293 

8  675 

8  220 

7  065 

6  163 

9  606 

9  101 

8.131 

8  140 

7  187 

6  187 

Difference  per  cent  

+  2.67 

+2.07 

+6.27 

+  0.'98 

—  1'.72 

—0.38 

The  Watt  indicator  should  give  us  the  pressure  in  the  interior  of  the 
cylinder  and  should  give  greater  values  than  the  pandynamometer,  as  the 
friction  of  the  packings  should  diminish  the  results  obtained  by  the  latter. 
This  difference  only  exists  on  September  29  and  October  28,  clearly  denned 
on  September  29,  but  for  all  the  other  experiments  is  reversed.  To  what 
cause  of  error  is  this  anomaly  to  be  attributed?  We  can  only  see  such  as 
may  be  caused  by  the  construction  of  the  apparatus  in  the  small  dimen- 
sions, a  little  piston,  strong  springs  and  too  high  a  speed  of  the  engine  giving 
results  which  have  not  the  exactness  wished.*  M.  Hirn  has  avoided  the 
oscillations  due  to  the  motion  of  springs,  and  notwithstanding  all  our  care 
with  the  indicator  the  pressures  are  too  low.  I  insert  the  diagrams  of 
boiler  pressure  taken  on  September  7,  in  which  they  are  notably  lower 
than  given  by  the  dynamometer.  But  the  greatest  error  with  these  two 
pieces  of  apparatus  does  not  exceed  2.4  per  cent,  of  the  work,  and  the 
indicator  is  valuable  in  practice  to  measure,  rapidly  and  closely,  the  power 
of  an  engine  in  motion;  in  certain  circumstances  it  can  serve  for  an  exact 

*Probably  leaky  piston  of  indicator  more  than  all  others,— C.  A.  S. 


THE  ALSA  TIAN  A'.V/'A' /,'/.)/ A  AT.S  K T< '.  2O5 

analysis,  as  in  the  case  of  compound  engines  making  20  to  30  revolutions 
per  minute.  In  this  case  the  uniformity  of  the  pressure  is  greater  than  in 
simple  engines,  which  is  favorable  to  the  indicator,  and  the  beam  dynamo- 
meter is  useless,  as  it  would  only  give  the  resultant  force  on  the  beam 
without  separating  the  effect  of  each  cylinder.  The  indicator  giving  the 
action  of  each  cylinder  permits  as  a  consequence  the  obtaining  of  the 
temperatures,  density,  internal  heat,  etc.,  of  the  working  steam  and  to 
follow  the  transfers  of  heat. 

THE   INFLUENCE  OF   THE   INTERNAL   SURFACES — THE   ERRORS  WHICH  MAY  BE 
COMMITTED    BY   NEGLECTING   THEIR  ACTION. 

We  believe  that  it  will  be  useful  before  commencing  this  study  to  recall 
briefly  some  preliminary  notions,  to  enumerate  some  of  the  facts  incon- 
testable in  themselves  but  of  which  the  consequences  have  been  violently 
discussed. 

Each  of  us  knows  that  the  cause  of  the  movement  of  engines,  the  force 
which  acts  through  the  medium  of  water  reduced  to  steam,  which  sets  in 
action  the  different  pieces  of  the  engine,  is  the  force  of  heat.  Heat  is  the 
direct  cause  of  the  movement.  The  first  study  naturally  imposed  upon  us 
is,  then,  the  phenomena  which  give  birth  to  the  action  of  this  force  upon  an 
intermediate  body.  Actually  completed  this  study  has  been  made  in  the 
cabinet  of  the  physicist  beyond  all  practical  applications,  and  holding  no 
account  of  the  circumstances  in  which  the  fluid  is  called  to  work. 

Assuming  that  there  is  no  interchange  of  heat  between  the  surface  of 
the  cylinders  and  the  fluid  which  they  contain,  considering  them  as  sim- 
ple geometrical  receptacles  impenetrable  to  heat,  is  evidently  contrary  to 
the  truth;  but  for  a  long  time  it  was  considered  that  the  errors  of  this 
theory  in  practice  could  be  neglected,  and  to  destroy  this  error,  to  prove 
how  far  it  was  from  the  reality,  a  series  of  precise  experiments,  so  well 
verified,  of  which  some  are  given  in  the  work  of  M.  Him,  was  needed,  to 
which  we  shall  add  others  which  we  will  develop. 

Without  doubt  it  is  possible  in  that  which  concerns  the  engine,  that  is 
to  say,  the  weight  of  steam  used  per  stroke,  to  directly  measure  it,  for  we 
have  checked  it  by  comparing  with  it  the  heat  used  and  rejected  by  the 
condenser,  directly  measured  also.  If  the  consumption  had  been  incor- 
rect this  error  would  have  exceeded  1  per  cent. 

If  we  desire  to  calculate  at  cut-off  and  the  end  of  the  stroke  the  weight 
of  dry  saturated  steam  inclosed  in  the  cylinder,  it  is  a  simple  matter. 

The  volume  swept  by  the  piston  and  the  densities  of  the  steam  are  all 
that  is  needed.  We  recall  the  diagrams  taken  with  the  indicator,  or  the 
pandynamometer,  where  the  abscissas  are  proportioned  to  the  stroke,  and 
seeing  how  clearly  the  intersection  of  the  curves  with  full  pressure  and 
with  expansion  are  defined  when  produced,  this  point  fixes  the  cut-off 
and  pressure  thereat.  To  the  volume  generated  by  the  piston  we  add  the 
clearance  volume  which  is  occupied  by  steam.  In  the  same  way  at  the 
end  of  the  stroke  the  last  ordinate  gives  the  pressure,  and  the-  clearance 


2O6 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


added  to  the  volume  generated  gives  the  volume  occupied;  the  same  could, 
of  course,  be  done  for  any  other  point  of  the  expansion. 

The  densities  are  obtained  by  two  relations,  one  established  by  Zeuner, 
a  direct  function  of  the  pressure, 

7    =    0.6061    P  0.9393j 

P  being  the  pressure  in  atmospheres,  the  other  a  function  of  temperatures 
and  therefore  indirectly  of  the  pressures,  the  corresponding  temperatures 
being  taken  from  the  tables  of  Regnault  or  the  formula  of  Roche,  deduced 
from  the  same  tables: 

1  1 


and  u  = 


(31.1  c  +  0.096  t  —  0.00002  *2.  —  0.000000 


J 
u  +  w  A  P 

where  w  is  the  volume  of  the  unit  of  water  and  u 


=  i',  that  of  the 
We  will  take  as  examples  the  calculations  rela- 


steam  7  =  -  =  density. 

tive  to  the  experiment  of  August  26,  1875,  cut-off  at  one-fifth. 

The  volume  swept  during  admission  augmented  by  the  clearance  is, 
i>0  =  0.1048  me.,  and  the  pressure  is  41,415  kgms.  per  sq.  metre,  whence  the 
density  is  y  =  2.5175  k.  The  weight  of  dry  steam  at  the  commencement 
of  expansion  is  m0  =  0.1048  me.  x  2.5175  k.  =  0.26383  k.,  while  the  feed  water 

per  stroke  was  0.2651  k.,  an  error  of  °-65i^  0.26383  _  legs  than  one.half 

0.2651 

of  one  per  cent.  Passing  to  the  end  of  the  stroke,  the  final  volume  in- 
cluding clearance  is  0.490  me.,  the  pressure  7,722  kgms.  persq.  m.,  whence 
we  have  a  density  -}\  =  0.46096  and  a  weight  of  steam  of  m1  =  0.490  me.  x 
0.46096  k.  =  0.21859  k.  ;  the  difference  is  17.5  per  cent.  What  has  become  of 
this  steam  which  has  disappeared  during  the  expansion?  We  hope  that 
the  examination  of  all  our  experiments  will  make  this  clear  to  all.  We 
place  them  in  the  following  tables  with  the  differences: 

TABLE  VII. 


s 

00 

0 

|j 

^j 

06 

gj 

«5 

> 

> 

M 

si 

•£ 

^ 

0 

§, 

< 

3 

i 

O 

Weight  of  feed  

0.3065 

0.3732 

0.2651 

0.2822 

0.2240 

0.2634 

0.  2265 

0.2982 

Weight  at  cut-off  mo  

0.28656  J0.2571 

0.26383 

0.2866 

0.1688 

0.1656 

0.22080.2625 

Difference    

9.01994:0.1124 

0.00217 

0.0044 

0.0552 

0.0948 

0.0057  0.0357 

Per  cent  

+6.5 

+  30.  4i     +0.83 

—1.5 

+24.64 

+36 

+2.52 

+  12 

Weight  at  end  of  stroke,  mi 

0.269810.2792    0.21859 

0.24496 

0.1761 

0.1707 

0.19060.2982 

0  0367  J0  094.0 

0  04651 

0.03724 

0.0479 

0  0927 

0.0359            0 

Percent  

+12 

+25.2 

+  17.5 

+  13.2 

+  21.38 

+  35.18 

+  15.  851           0 

We  find  their  marked  differences  nearly  always  less  between  the  calcu- 
lated and  measured  weights.  What  are  the  causes?  Let  us  review 
them. 

For  those  who  know  how  difficult  it  is  to  keep  a  metal- packed  piston 
tight,  nothing  is  more  simple  than  to  suppose  leakage.  To  those  who 
have  not  learned  all  the  arrangements  adopted,  we  explain  that  it  is  easy 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  2O7 


to  make  a  tight  piston.  Suspending  the  piston  and  with  two  cast-iron  rings 
sprung  in  make  a  tight  piston.  But  in  many  cases  a  vertical  cylinder 
cannot  be  used.  We  believe  that  the  piston  rod  should  be  carried  at 
both  ends  of  the  cylinder,  to  avoid  leaks,  and  to  use  softer  cast-iron  for 
the  rings  than  for  the  cylinder. 

What  is  important  for  us  is  to  see  that  the  vertical  engine  on  which  we 
experimented  possessed  a  tight  piston,  and  that  the  natural  hypothesis  of 
leakage  is  inadmissible. 

How  could  we  believe  that  these  losses  could  give  an  increase  over 
that  directly  gained,  for  example  on  August  27,  and  how  could  the  piston 
of  the  same  engine,  working  with  almost  the  same  initial  pressure,  vary 
from  0.83  to  36  per  cent,  in  a  few  days,  August  26  to  September  7  and  8.; 
or  from  25  to  36  per  cent,  from  September  7  to  September  8?  There  is  no 
doubt  that  all  conditions  were  the  same,  except  the  superheating,  and  we 
should  suppose  that  the  hotter  steam  would  leak  the  easier;  on  the  con- 
trary the  leakage  is  least  then. 

Finally,  we  will  note  some  results  which  will  support  the  views  we 
shall  advance,  knowing  that  the  piston  was  tight. 

It  will  be  remarked  that  in  the  table  given  there  is  for  many  of  the 
experiments  less  steam  accounted  for  at  the  end  of  the  stroke  than  at  the 
cut-off.  On  November  28  it  decreases  from  30.4  to  25.2  per  cent.,  and  on 
September  7  from  24.64  to  21.38  per  cent.,  but  in  the  non- condensing  run 
of  October  28  it  changed  from  12  to  0  per  cent,  at  the  end  of  the  stroke. 

Let  us  recall  the  progress  of  the  steam  in  the  engine,  and  see  if  this  is 
not  an  impossibility  with  a  leaky  piston. 

The  consumption  per  stroke  was  measured  with  all  the  precautions 
stated  above;  it  is  then  the  weight  of  fluid  which  passes  through  the 
cylinder,  leakage  or  no  leakage.  The  computation  based  on  the  volume 
and  density  gives  the  actual  quantity  of  steam  present.  Is  the  difference 
lost?  If  so,  how  explain  the  irregularity  in  amount,  or  the  excess  in  some 
cases?  Every  one  must  see  that  this  is  absurd,  and  the  hypothesis  of  leak- 
age cannot  be  maintained.  One  of  the  most  important  propositions  of 
applied  physics  gives  us  the  key. 

When  steam  is  introduced  into  a  reservoir  of  invariable  dimensions,  of 
which  the  surface  has  not  everywhere  the  same  temperature,  the  final  pressure 
of  the  steam  is  that  which  corresponds  to  the  lowest  temperature. 

It  was  upon  the  facts  from  which  this  proposition  is  deduced,  that 
Watt  based  one  of  his  best  discoveries,  the  condenser;  it  will  serve  us  to 
explain  the  apparent  disappearance  of  the  steam  which  we  have  stated. 

The  study  of  the  phenomena  to  which  the  action  of  heat  upon  water 
gives  birth  has  been  made  in  the  cabinet  of  the  physicist,  ignoring  at  the 
start  perturbing  influences.  The  results  thus  obtained  are  as  exact  as  the 
laws  from  which  they  are  derived,  and  if  we  have  an  error  to  note,  at  least 
it  is  not  from  applying  erroneous  principles.  We  will  not  repeat  too  much, 
transporting  to  the  domain  of  practice  the  physical  data  relative  to  steam, 
without  considering  the^circumstances  in  which  the  steam  is  called  to 


208  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

work.  Kegarding  engine  cylinders  as  simple  geometric  receptacles  im- 
penetrable to  heat,  of  stating  that  there  is  no  exchange  of  heat  between 
the  steam  and  its  surrounding  metal,  is  from  all  evidence  contrary  to  the 
truth  and  has  never  been  sustained.  But  for  a  long  time  it  has  been  im- 
plicitly considered  that  the  various  errors  arising  from  this  supposition 
were  insignificant.  We  shall  see  if  it  is  possible  to  neglect  them. 

Kemarking,  first,  that  when  the  steam  is  taken  directly  from  the  boiler, 
experiments,  November  28,  1873,  and  September  8,  1875,  as  is  usually  the 
case,  we  have  to  do  with  a  vapor  in  contact  with  its  liquid,  a  so-called 
saturated  vapor,  that  is  to  say,  in  such  a  state  of  equilibrium  that  it  is 
impossible  to  take  away  the  smallest  quantity  of  heat  without  condensing 
a  portion,  that  almost  always  the  gas  itself  has  entrained  and  mixed  with 
itself  a  portion  more  or  less  great  of  the  fluid  from  which  it  came.  Neg- 
lected for  the  two  experiments  which  occupy  us  it  is  sometimes  5  or  6  per 
cent,  of  the  weight  of  steam  introduced.  In  this  condition  it  is  impossi- 
ble to  add  heat  without  evaporating  a  part  of  the  fluid  in  suspension. 

This  state  of  saturation  or  unstable  equilibrium  of  a  vapor  mixed  with 
its  liquid  in  more  or  less  quantities  is  such  that  any  addition  or  subtrac- 
tion of  heat,  how  small  soever  it  may  be,  brings  immediately  and  neces- 
sarily the  evaporation  or  condensation  of  the  liquid  or  vapor.  In  such  a 
condition  does  the  mixed  fluid  pass  from  the  boiler  to  the  cylinder. 

At  the  end  of  the  steam  pipe  it  finds  in  the  steam  chest  the  valve  open 
to  the  cylinder,  the  piston  at  or  near  the  end  of  the  stroke,  and  the  steam 
then  fills  the  clearance  spaces  between  the  valve  and  the  piston.  In  the 
engine  we  are  studying  the  clearance  is  5  litres,  very  small  relatively  to  the 
inclosing  surfaces,  the  cylinder  head  and  piston  have  0.5699  sq.  in.,  and  are 
instantly  filled;  the  steam  is  thus  brought  against  an  extended  surface 
which  has  been  cooled  during  the  preceding  strokes  by  the  expansion 
and  the  exhaust  to  the  condenser.  The  incoming  fluid  tends  to  impart  its 
temperature  to  the  surfaces,  and  a  large  portion  condenses,  yielding  its 
heat  of  evaporation.  By  virtue  of  the  proposition  enunciated  above,  the 
pressure  of  the  fluid  would  fall  if  the  communication  from  the  boiler  was 
not  open  and  did  not  permit  a  constant  influx  of  steam  coming  to  replace 
that  liquified  till  the  moment  that  the  interior  of  the  cylinder  has  acquired 
the  temperature  due  the  pressure. 

All  these  phenomena  are  produced  in  the  almost  inappreciable  inter- 
val of  time  the  piston  is  at  the  end  of  the  stroke,  and  afterward  the  piston 
uncovers  fresh  cooled  surface  which  also  condenses,  but  much  less  rapidly 
than  than  at  the  first  instant,  for  whatever  be  the  speed  of  the  piston  at 
midstroke  the  surface  is  much  less  in  proportion  to  the  inclosed  volume 
than  at  the  end  of  the  stroke.  Finally  the  valve,  after  opening,  closes  the 
steam  port  and  the  expansion  commences  without  interrupting  the  action 
of  the  surfaces,  but  the  supply  of  heat  from  the  boiler  being  ended  the 
reverse  action  begins,  while  at  the  same  time  steam  is  condensing  on  the 
cool  surface  uncovered  by  the  piston  it  is  forming  from  the  heads  which 
had  been  previously  warmed. 

Take  the  experiments  of  November  28  and  September  8  made  with 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  2O9 

saturated  steam.  When  the  expansion  commences,  we  have  shut  up 
in  the  cylinder  a  mixture  of  69.6  per  cent,  steam  and  30|  per  cent, 
water  in  one  case;  64  per  cent,  steam,  and  33  per  cent,  water  in  the 
other. 

This  water,  as  we  have  shown  before,  came  nearly  all  from  direct  con- 
densation on  the  metal;  it  is  deposited  on  the  surface  lining  it  and  pos- 
sessing its  temperature  and  that  of  the  steam  in  the  cylinder.  The  piston 
advances,  the  work  of  expansion  demands  a  certain  quantity  of  heat,  the 
fresh  cool  surface,  uncovered,  condenses  more  steam,  the  pressure  falls, 
and  the  water  lining  the  surfaces  instead  of  increasing,  grows  less  or  re- 
mains the  same  in  quantity,  25.2  per  cent,  instead  of  30.4  per  cent,  and 
35.19  per  cent,  instead  of  36  per  cent.  This  shows  clearly  that  evaporation 
has  been  produced  from  the  surfaces  which  first  condensed  and  were 
then  warmed  by  the  steam . 

During  the  expansion  the  pressure  and  temperature  fall  at  each  instant. 
The  cylinder  surface  and  water  covering  it,  keep  at  each  instant  a  temper- 
ature little  higher  than  that  of  the  steam,  but  at  each  instant  this  temper- 
ature tends  to  equality  with  that  of  the  mass  of  steam,  which  can  only 
occur  through  the  medium  of  the  deposited  water  evaporating  at  the 
expense  of  its  own  heat,  or  yielding  its  excess  to  the  metal,  or  drawing 
from  it.  The  steam  and  condensed  liquid,  evaporating  or  condensing, 
serve  as  the  vehicle  of  heat  so  well  that  at  the  end  of  the  stroke  we  have 
different  proportions  from  those  at  the  end  of  admission. 

All  this  concerning  the  vapor  of  saturated  steam  is  only  the  natural 
consequence  of  the  laws  of  the  transmission  of  heat,  and  it  is  matter  of 
astonishment  that  it  has  been  contested;  not  that  the  principle  has  been 
denied,  but  it  has  been  called  insignificant  in  its  influence  from  the  fact 
that  gases  are  bad  conductors  of  heat,  and  assuming  the  time  of  a  stroke 
to  be  too  short  to  permit  any  considerable  exchange  of  heat  by  radiation, 
we  have  come  to  see  that  it  is  by  direct  contact  and  not  by  radiation  that 
this  action  can  condense  up  to  36  per  cent.  In  this  case  the  error  would 
be  in  not  taking  account  of  the  action  of  the  surfaces:  it  is  far  from  being 
one  that  may  be  neglected,  as  it  has  been. 

Let  us  see  what  happens  when  the  steam  from  the  boiler  by  a  special 
apparatus  has  its  temperature  raised  about  100°  C.  above  that  of  saturated 
steam  when  it  is  superheated.  Brought  in  that  state  to  the  cylinder,  one 
can  believe  that  it  will  act  as  a  gas,  losing,  without  doubt,  its  heat,  its 
superheat,  but  never  falling  below  that  of  saturated  steam.  The  experi- 
ment of  September  7  shows  us  the  contrary,  that  steam  at  195°  C.  can  con- 
dense on  the  surface,  giving  24.64  per  cent,  of  water,  and  the  heat  of 
evaporation  of  this  water  is  given  to  the  metal,  besides  the  superheat, 
which  it  gives  first.  When  the  expansion  commences  there  is  then  only 
saturated  steam  containing  one-fourth  water  in  the  cylinder,  most  of  the 
water  being  on  the  surfaces.  We  are  in  identical  conditions  with  the 
experiment  of  November  28  and  September  8.  All  the  phenomena  we 
have  already  described  take  place.  Condensation  and  evaporation  going 
on  simultaneously  in  different  parts  of  the  cylinder,  we  find  at  the  end 


210  STEAM  USING;   OR,  STEAM  ENGINE  PRACTICE. 


of  the  stroke  21.38  per  cent,  water,  showing  that  3  per  cent,  has  been  re- 
evaporated. 

Between  this  experiment  and  that  of  November  28,  one  with  super- 
heated steam  and  the  other  with  saturated  steam,  the  analogy  is  striking. 
It  is  far  from  being  so  with  the  others,  which  appear  almost  in  part  as 
exceptions  to  the  laws  which  we  state. 

On  September  29,  and  August  26  and  27,  the  condensation  at  the  begin- 
ning of  expansions,  2.52  per  cent,  and  0.83  per  cent.,  are  very  small,  and 
on  August  27  the  steam  remained  superheated,  since  the  weight  of  steam 
calculated  is  greater  than  that  directly  measured.  To  give  an  account  of 
what  passes  let  us  recall  what  we  said  in  our  two  experiments  with  satu- 
rated steam. 

At  the  commencement  of  the  stroke  only  the  clearance  space  is  open 
to  the  incoming  steam.  The  condensation  is  then  very  energetic;  we  can 
perhaps  say  that  nearly  all  the  steam  which  comes  first  is  liquified  against 
the  metallic  surface,  whether  it  be  superheated  to  223°  C.  or  not,  for  what 
is  the  heat  of  superheating  compared  with  the  weight  of  surrounding  metal 
to  be  warmed,  and  the  steam  first  introduced  into  the  clearance  space  is 
small  in  amount  of  heat  compared  with  the  quantity  to  be  given  up.  The 
steam  then  introduced  instantly  loses  its  superheat  and  the  piston  begins 
to  move.  We  have  then  saturated  steam  in  contact  with  a  large  portion  of 
water,  which  we  unfortunately  cannot  directly  determine,  but  of  which  we 
can  affirm  the  existence,  for  our  experiments  proved  that  the  proportion 
of  water  liquified  was  very  considerable,  though  the  time  was  very  short, 
that  is  to  say,  with  the  surface  increased  inversely  as  the  weight  of  steam 
introduced,  we  could  bring  it  all  to  water.  The  piston  then  moves  more 
and  more  swiftly,  and  steam  flows  in  from  the  boiler  through  the  super- 
heater at  a  temperature  of  223°  C. ;  it  meets  the  saturated  steam,  with  which 
it  mixes,  then  the  water  covering  the  surfaces  and  yielding  heat  to  it  evapo- 
rates it  so  well  that  on  August  27  the  whole  was  superheated,  since  the  cal- 
culated weight  of  steam  at  the  end  of  admission  was  one  per  cent,  greater 
than  the  gauged  weight  per  stroke.  At  other  times,  since  the  weight  com- 
puted is  little  greater  than  measured,  the  difference  being  with  the  errors 
of  observation,  we  will  therefore  suppose  the  vapor  saturated  but  dry. 
During  the  expansion  we  see  that  the  liquif  action,  in  spite  of  an  introduction 
of  nearly  half  stroke,  reaches  13  per  cent,  at  the  end  of  the  stroke.  A  con- 
densation takes  place  because  the  surface  originally  warmed  did  not  receive 
heat  enough  to  prevent  it.  This  is  shown  by  the  experiments  of  August 
26  and  September  29,  and  for  November  18. 

We  then  arrive  at  the  last  of  our  experiments,  remarkable  as  we  shall 
see,  in  analyzing  that  of  October  28  at  high  pressure  non- condensing.  The 
steam  heated  to  220°  C.  is  admitted  for  one- quarter  of  the  stroke,  expands 
to  one  atmosphere  and  is  exhausted  into  the  air. 

The  clearances  of  the  engine  we  are  studying  are  5  litres,  say  1  per 
cent,  of  the  cylinder  volume.  We  have  in  our  preceding  experiments 
neglected  the  weight  of  steam  shut  up  at  the  closing  of  the  exhaust.  With 
low  pressure  and  density  the  weight  may  be  neglected,  but  such  is  not 


THE  ALSATIAN  EXPERIMENTS,  ETC.  211 

the  case  when  the  exhaust  is  at  the  atmospheric  pressure.  The  compressed 
steam  rises  even  above  the  pressure  of  admission,  and  its  weight  is  0  0268 
k.,  say  10  per  cent,  of  that  consumed  per  stroke. 

It  is  easy  to  obtain,  as  we  know  the  closing  of  the  exhaust  valve,  the 
pressure  and  volume.  We  then  find  the  density  a  function  of  the  pressure. 
As  this  steam  at  this  point  is  dry  and  saturated,  as  we  shall  see,  its  weight 
represents  the  whole  steam  in  the  cylinder,  a  quantity  put  into  the  cylin- 
der at  the  first  revolution  and  in  a  manner  remaining  there  till  the  engine 
is  stopped;  but  if  this  weight  is  constant  its  temperature  is  not,  for  it  par- 
ticipates along  with  the  new  steam  in  all  the  exchanges  of  heat  of  which 
the  engine  is  the  seat. 

The  first  action  is  daring  the  cushion  and  before  the  steam  valve  opens. 
The  weight  calculated  at  the  closing  of  the  exhaust  was  0.0268  k.  of  steam 
that  we  know  to  be  dry.  If  we  value  it  again  when  it  only  fills  five  litres 
of  the  clearance  volume  we  find  only  0.0093  k.;  the  balance  has  been  con- 
densed upon  the  surfaces,  having  a  lower  temperature  than  the  compressed 
vapor,  of  which  the  pressure  is  constantly  increasing.  Then  the  steam 
valve  opens,  and  steam  rushes  in  and  mixes  with  that  compressed,  aban- 
doning its  superheat  and  at  the  end  of  admission  containing  12  per  cent, 
of  water.  The  expansion  commences,  and  at  the  end  of  the  stroke  the 
deposited  water  has  evaporated,  and  we  have  dry  steam. 

Summing  up,  the  examination  of  each  of  our  experiments  brings  us 
to  the  conclusion  that  we  can  by  no  means  neglect  the  action  of  the  sur- 
faces. To  a  certain  depth  the  metal  of  the  cylinder  is  penetrable  by  heat; 
it  plays  the  role  of  a  reservoir,  which  receives  heat  during  admission  and 
gives  it  out  during  expansion,  or  continues  to  receive  but  gives  it  out 
again  during  exhaust.  This  action  is  shown  clearly  by  the  figures  in  Table 
VII.  There  we  find  the  proportion  of  water,  which  sometimes  could  be 
neglected,  following  the  conditions  under  which  the  experiments  have 
been  made.  Thus  with  steam  superheated,  cut-off,  •*,  £  and  throttle,  the 
condensations  are  1  per  cent.,  2  per  cent.,  and  even  superheated;  while 
with  saturated  steam,  cut-off  \,  we  find  water  25  per  cent.,  30  per  cent,  and 
36  per  cent. 

Above  all,  this  series  of  eight  experiments  removes  all  doubts,  and  it 
no  longer  can  be  denied  that  these  exchanges  of  heat  actually  take  place, 
variable  in  intensity  and  intimately  connected  with  the  conditions  of  tem- 
perature and  expansion  in  which  the  engine  is  worked. 

Cooling  due  to  the  Condenser. — We  can  enumerate  the  various  changes 
to  which  the  steam  submits  during  its  passage  through  the  cylinder,  fol- 
lowing the  exchanges  of  heat  upon  the  surfaces  or  in  the  fluid  inclosed  by 
them;  this  is  not  the  only  question,  but  only  the  first  step  in  the  road  to 
which  our  analysis  has  led  us,  for  we  can  find  not  only  the  manner  of 
the  distribution  of  heat,  but  the  exact  values  by  obtaining  that  which  is  con- 
sumed on  the  one  side  by  work  done,  and  on  the  other  the  various  losses 
produced  during  expansion  and  exhaust.  This  study  requires  us  to  refresh 
our  memory  with  some  of  the  facts  established  by  thermodynamics,  among 
others  what  is  meant  by  the  internal  heat  U  of  a  mixture  of  steam  m  and 


212 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


water  M  —  m,  this  value  £7"  is  the  total  heat  of  the  mixture  less  that  of  the 
external  A  Pu;  it  is  expressed 


U  =  l-APu  =  M 


cdt  +  mp 


U=  M  (t  +  0.00002  *2  -f  0.0000003  J3)  +  m  (575  —  0.791  *)• 
From  the  elementary  principles  of  thermodynamics  the  value  of  U 
can  only  vary:  1.  If  the  total  mass  M  does  external  work,  positive  or 
negative,  augmenting  or  diminishing  in  volume  under  an  external  pressure, 
and  then  the  variation  of  U  is  proportioned  to  the  work  done.  2.  lithe 
mass,  without  doing  work,  receives  or  loses  heat  by  contact  with  any  other 
body.  3.  It'  these  two  phenomena  take  place  together;  in  this  case  the 
change  in  U  may  be  zero.  We  know  the  heat  consumed  by  the  work  of 
expansion,  since  this  is  given  by  the  diagrams,  and  it  suffices  to  divide  the 
number  of  kilogrammetres  by  425  to  have  this  quantity  in  heat  units. 
Putting  then  the  internal  heat  [7  and  the  work  of  expansion  AF"  we  have: 

TABLE  VIII. 


CC                      00 

so 

jj 

. 

00 

3 

.    rf 

>         > 

bt 

A 

t 

i 

« 

^ 

fc          fc 

* 

3 

02 

02 

02 

O 

Internal  heat  at  cut-off 

£/o   G  

'  176.81    173.92 

160.42 

169.94 

110.22 

114.19 

133.10 

163.73 

Internal    heat    at  end  of 

stroke,  U±         

164.44    175  79 

134.37 

149.42 

108.26 

109  .07 

116.28 

117.91 

Difference  

+  12.37    —1.87 

+  26.05 

+20.52 

+1.566 

+5.12 

+  16.82 

—14.24 

Heat  given  to  iron  

23;26;     57.73 

9.84 

11.56 

33.95 

48.10 

14.80 

29.40 

Work  of  Exp.  A  FA  

16.521     15.835 

15.79 

9.24 

14.31 

13.70 

7.22 

14.50 

In  this  table  we  also  give  the  heat  which  the  fraction  M  —  m  gives  to 
the  metal  during  admission,  by  condensing  upon  the  surfaces  increased  by 
the  superheat  lost  by  the  mass  M,  we  shall  call  it  the  heat  stored  by  the 
surfaces. 

The  internal  heat  U  sometimes  increases,  or  diminishes,  or  remains 
nearly  stationary.  Let  us  examine  each  case. 

1.  On  October  28  it  is  14.24  c.  more  at  the  end  than  the  beginning  of 
the  expansion,  and  there  has  also  been  done  14.5  c.  of  external  work  which 
should  have  been  at  the  expense  of  the  internal  heat  U  and  this  should 
have  decreased  instead  of  increased.  This  must  have  had  heat  from  out- 
side, and  as  the  boiler  is  cut-off  it  must  have  come  from  the  cylinder 
metal,  and  as  there  is  no  jacket  the  metal  must  have  taken  it  from  the 
incoming  steam  as  previously  explained.  The  metallic  surface  has  con- 
densed a  portion  of  the  steam  brought  from  the  boiler,  the  temperature  is 
raised  and  the  heat  penetrates  the  metal  to  a  depth  more  or  less,  but  which 
matters  little;  it  in  a  manner  stores  up  heat  which  we  can  value  directly 
from  the  superheating,  M  x  0.5  (6  —  t)  =  0.2717  k.  x  0.5  (220°  —  137.49°)  = 
11.20  c.;  where  M  =  the  mass,  0.5  —  specific  heat  of  steam,  6  =  temper- 
ature of  steam,  t  =  temperature  of  saturated  steam  at  same  pressure.  To 


THE  A  L  >  - 1  77. 1  A"  K XPE  /,'/.!/ K XTS,  E TC.  213 


this  value  is  added  the  heat  obtained  from  condensing  0.0357  k.  liquified 
during  admission. 

0.0357  k.  x  r  =  0.0357  X  509.78  c.  =  18.29  c. 
11.20  x  18.20  =  29.40  c. 

The  work  of  expansion  was 14.60  c 

The  external  radiation  was 2.50  c 

The  increase  in  internal  heat  was 14.24  c 

Total 31 . 24  c 

being  with  1.84  c.  of  the  other,  an  error  of  less  than  1  per  cent,  of  the 
186.72  c.  brought  to  the  cylinder. 

2.  When  the  variations  of  internal  heat  are  very  small,  November  28 
and  September  7,  for  example,  we  may  consider  it  as  remaining  nearly 
stationary  during  the  expansion,  and  the  external  work  done  during  ex- 
pansion must  have  been  furnished  by  the  metal  and  not  by  the  internal 
heat;  the  metal  must  have  received  it  during  admission,  but  this  is  only  a 
portion  of  their  action,  for  if  we  compare  the  amount  the  surface  has  re- 
ceived 33.95  c.  on  September  7,  when  the  work  of  expansion  is  14.31,  the 
external  radiations  2.50,  leaving  18.80  c.  to  be  accounted  for  per  stroke — 
what  has  become  of  them?  Given  to  the  surface  per  stroke  it  is  impossible 
to  have  them  remain  there,  for  the  temperature  would  rise  to  such  a  point 
as  to  melt  the  iron  under  an  increase  of  heat  of  18.80  c.  per  stroke;  they 
must  have  gone  to  the  condenser  during  exhaust  unless  the  piston  leaked, 
and  we  showed  above  that  it  was  tight.  The  difference  we  call  Re,  refrig- 
eration by  the  condenser.  It  is  the  form  first  known  of  the  action  of  the 
internal  surfaces,  an  influence  long  doubted  and  far  from  being  admitted 
in  our  day.  We  refer  to  table  VII.,  and  find  there,  except  for  the  non- 
condensing  experiment,  that  there  is  from  12  to  35  per  cent,  of  water  at 
the  end  of  the  stroke  whether  it  entered  saturated,  wet,  or  superheated,  the 
result  of  all  the  exchanges  of  heat  being  the  condensation  of  a  greater  or 
less  portion  of  the  steam  which  works.  This  action  is  due  to  the  sides  cov- 
ered with  a  layer  of  water  very  thin  and  at  the  temperature  of  the  metal. 

When  the  exhaust  valve  opens  the  steam  rushes  out,  its  pressure  falls 
rapidly,  and  its  temperature  still  faster  till  it  reaches  that  of  the  water  in 
the  condenser,  this,  in  the  cylinder  in  spite  of  the  smallness  of  the  connect- 
ing passages,  and  the  temperature  is  lower  than  that  at  the  end  of  the 
stroke;  but  the  surfaces  of  the  cylinder  and  the  water  which  covers  them 
are  higher  in  temperature  and  the  water  upon  them  evaporates,  and  the 
heat  is  taken  from  the  metal  in  which  it  had  accumulated  during  admis- 
sion. 

We  see  here  the  reverse  of  the  phenomena  during  admission,  the  sur- 
faces cooled  during  exhaust  are  warmed  by  the  incoming  steam  which 
they  condense  and  evaporate  during  exhaust,  and  are  again  cooled.  These 
two  opposing  actions  are  the  result  of  the  same  physical  cause,  the  per- 
meability to  heat  of  the  surfaces  and  that  which  they  inclose. 

If  even  to-day,  resting  upon  the  poor  heat-conducting  power  of  gase- 
ous fluids  and  the  shortness  of  time,  it  is  believed  that  the  effect  of  the 


214 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


surfaces  can  be  neglected,  the  following  table  will  again  prove  that  it  is 
not  small,  that  the  cylinder  loses  during  exhaust  a  certain  number  of 
calories  which  are  far  from  being  small,  and  which  do  no  work  whatever, 
and  which  even  exceed  those  expended  in  the  work  done. 

As  we  have  seen,  the  values  of  Re  are  deduced  from  the  very  simple 
relations  of  the  internal  heat,  the  work  done  and  the  heat  given  up  to  the 
metal  during  admission. 

r  (M—m)  =  C/i  —  U0  +  A  F.  +  2.5  c.  +  .Re. 

For  September  7,  33.95  c.=  —  1.66  +  H.31  +  2.5  c.+  .Re. 
Re  =  35.61  —  16.81  =  18.80  c. 

But  these  values  can  be  checked  by  a  different  computation,  which  we 
shall  follow  out,  knowing  that  Re  is  the  heat  taken  from  the  iron  during 
exhaust. 

If  this  heat  is  retained  in  the  metal  up  to  the  opening  of  exhaust,  it 
will  not  be  in  the  final  internal  heat  at  the  end  of  the  stroke  Uv,  but  we 
shall  find  it  increased  by  the  work  of  expulsion,  in  the  water  rejected 
from  the  condenser,  and  the  difference  will  give  it  to  us.  For  September 
7,  Ul  =  108.56  c.,  less  that  remaining  after  condensing  6.81,  added  to  the 

back  pressure  work  2.14  c.  gives 103.89  c. 

The  heat  found  in  condenser  is 122.77  c. 

Difference,  Re '. 18.88  c. 

The  other  method  gave 18.80  c. 


Error 


0.08  c. 


TABLE  IX. 


Rc  1st  method ,  15.61!  37.53 

Reid.  i  15.79!  35.33 

Error i     0.82      2.20 

Total  heat  per  stroke |212.31  241 .36 

Rc  per  cent,  of  this !    7.80   15.60 


*  i 

bi 

0 

<J 


17.60  20.34;  18.80|  37.02  21.90  1.84 
17.03  19.66  18.88  37.37  20.09  £  p, 

0.57  0.68  0.08  0.35  1.81:  «£  bl 
181. 56  194. 36  151. 15  170. 00  154.  lO^q  .2 

9.701  10.50    12.43!  21.76    14. 21 I      8  " 


Here  again  it  is  not  easy  to  construct  any  gratuitous  hypothesis  The 
explanation  we  have  given  of  the  observed  phenomena  is  based  upon  pre- 
cise figures.  It  is  the  expression  of  the  truth.  We  state  from  direct  ob- 
servation that  the  surfaces  inside  the  cylinder  are  covered  with  a  water 
film,  condensed  from  dry  or  even  superheated  steam.  This  water  upon 
the  surface  at  a  temperature  greater  than  the  exhaust  is  evaporated  and 
carries  away  from  the  iron  a  certain  quantity  of  heat  which  is  taken  again 
from  the  boiler  during  the  admission  at  the  next  stroke.  The  consequence 
is  that  during  admission  it  condenses  steam  enough  to  do  the  work  of 
expansion,  and  more  yet  the  external  radiation,  and  the  internal  radiation, 
to  the  condenser  Re,  and  we  can  also  value  this  Re  in  two  ways,  and  the 


THE  A  L  SA  T1A  N  EXPEB1MENTS,  E  TC.  215 

greatest  error  has  been  1.84  or  1.17  per  cent,  of  the  heat  used  by  the  engine 
per  stroke. 

vlf  I  insist  upon  this  point,  it  is  because  this  value  Re  has  been  not  only 
discussed  but  badly  understood  by  some  engineers  who  have  found  for 
Be  large  negative  values,  and  who  have  tried  to  give  a  reason  for  this 
anomaly  which  was  simply  due  to  an  error  of  observation  as  the  only 
negative  value  under  exceptional  circumstances,  that  we  have  in  our  table. 
In  a  word,  any  negative  value  of  Re  is  absurd. 

3.  The  internal  heat  diminishing  to  the  end  of  the  stroke  in  this  case, 
the  loss  of  internal  heat  added  to  that  stored  by  the  surfaces  goes  into  the 
work  of  expansion  and  into  the  external  radiation,  and  any  excess  is  lost 
by  the  cooling  by  the  condenser,  Re,  which  is  found  as  before. 

The  water  present  in  the  steam  at  the  end  of  the  stroke  is  the  cause  of 
the  phenomena  we  are  studying.  Nothing  is  easier  than  to  see  that  the 
figures  of  our  table  are  closely  connected  with  the  final  proportion  of 
water  varying  with  it.  Even  the  Re  =  — 1.84  c.,  that  is  within  1  per  cent,  of 
nothing  for  the  non- condensing  experiment,  for  which  the  steam  is  dry  at 
the  end  of  the  stroke;  but  this  case  is  uncommon.  If  we  admitted  that 
Re  could  be  negative,  it  would  only  be  saying  that  the  condenser  was 
sending  heat  to  the  cylinder  in  the  place  of  cooling  the  steam  contained 
in  it.  The  second  method,  serving  as  a  check,  could  only  give  Re  nega- 
tive, by  having  too  large  a  value  of  U^  after  accounting  for  the  work  of 
expulsion,  but  as  this  internal  heat  is  all  that  the  steam  contains  after 
having  worked  in  the  engine,  we  should  at  least  find  that  in  the  water  of 
condensation.  If  the  observation  gives  us  a  quantity  too  small,  some  heat 
must  have  been  lost  between  the  cylinder  and  the  point  at  which  the 
measurement  is  made;  this  can  only  be  produced  by  leakage,  but  one  could 
easily  detect  that,  for  it  could  only  be  in  the  exhaust  pipe,  or  by  the  loss 
of  heat  by  conduction  from  a  very  moderately  heated  pipe  70°  or  80°  C. 
only. 

Kesuming,  this  loss  Re  unexplained  and  neglected  in  the  study  which 
denies  the  action  of  the  surfaces,  which  may  reach  22  per  cent,  of  the 
steam  used,  constitutes  a  useless  expense  which  merits  attention  and  for 
which  we  should  seek  a  remedy. 

At  the  point  to  which  we  have  attained  in  our  analysis  there  should  no 
longer  remain  any  doubt  in  the  minds  of  our  readers  of  the  action  of  the 
internal  surfaces  of  the  cylinder;  but  it  may  be  useful  before  quitting  the 
subject  to  show  how  errors  committed  in  the  account  of  steam  can  extend 
in  the  account  of  work;  to  see  if  the  steam  condensed  during  admission 
really  corresponds  1st,  to  the  external  work  of  expansion;  2d,  to  the  exter- 
nal radiation,  and  3d,  to  the  internal  radiation  during  exhaust. 

Thermodynamics  establishes  the  general  equation 

dQ  =  Mcdt  +  dmr  —  ™  dt 

which  connects  the  quantity  of  heat  d  Q  at  each  instant  with  the  mass 
m  of  steam  and  M  —  m  of  water  inclosed  in  the  cylinder,  the  heat  of 


216 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


evaporation  r,  the  absolute  temperature  T  and  the  specific  heat  c  of  the 
liquid. 

Since  in  whatever  manner  the  heat  Q  has  been  added  to  or  subtracted 
from  the  work  of  expansion,  A  Ft  —  Q  +  ( Z70  —  t/i)  the  internal  heat  at  the 
beginning  and  end  of  expansion  is  known  from  the  temperatures  and 
pressures.  Proceeding  thus,  the  expansion  curve  is  verified  from  its  two 
ends. 

But  for  Q  we  find  ourselves  in  the  presence  of  two  theories.  The 
generic  theory  of  the  engine  with  non-conducting  cylinder,  and  the  other 
called  the  practical  theory,  which  admits  the  action  of  the  surfaces  as  a 
reservoir  of  heat.  We  shall  see  under  another  form  which  answers  to  the 
facts.  Denying  the  action  of  the  surfaces  in  stating  that 

dQ  and  Q  =  0,  or,  AFA  =  U0  —  Uv\ 
Tabulating  these  values  for  all  our  experiments  we  have 


GO 

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K 

s 

t-^ 

00 

£ 

s 

> 

> 

bi 

M 

ft 

Q 

a 

4J 

g 

1 

1 

f 

4 

I 

6 

CD 

0> 
GO 

1 

£T0_  JJ    c  _ 

+12  37 

—1  870 

+  26  05 

+  20  52 

+1  66 

+5.12 

+16  82 

—14.24 

AFdC 

16  52 

15  835 

15  79 

9  24 

14  31 

13  17 

7  22 

14.50 

Differences  c  

+  4.15 

+  17.705 

—10.  26 

—11.  '28 

+12.65 

+  8.58 

—9.60 

+28.74 

The  figures  of  this  table  are,  as  we  see,  very  eloquent;  there  is  even 
the  absurdity  of  negative  work  on  November  28  and  October  28,  for  in- 
stance, and  the  generic  theory  is  untenable. 

We  have  to  return  to  the  equation 


dQ  =  Mcdt  +  dmr  — 


mr 


and  sum  these  quantities  during  the  expansion  to  find  a  function  which 
may  be  integrated.  M.  Hirn  has  arrived  at  it  by  a  very  natural  idea  which 
he  developes  as  follows: 

"After  many  fruitless  researches  I  decided  to  return  here  in  the  track 
traced  by  the  experimental  method  itself.  As  the  action  of  the  surface 
consisted  not  only  in  taking  heat  from  or  yielding  it  to  a  gaseous  mass, 
but  in  partially  condensing  a  mass  of  saturated  vapor,  or  of  evaporating 
partially  a  mass  of  water  in  contact  with  it,  I  thought  that  the  hypothesis 
nearest  truth  would  consider  the  active  part  of  the  surface  as  a  portion  of, 
and  at  the  temperature  of,  the  water  covering  it.  Whatever,  in  reality, 
may  be  the  temperature  of  the  surface,  the  water  covering  and  evaporat- 
ing or  condensing  must  be  at  the  temperature  of  the  saturated  steam. 
The  exactness  of  this  view  has  been  fully  sanctioned  by  experience. " 

We  can  always  represent,  by  a  proper  weight  of  water  at  temperature 
T,  varying  by  dT,  the  position  of  the  mass  of  the  surface  which  is  warmed 


THE  A  L  S-.-l  77. 1  .V  EX PE111MEXTX,  ETC.  217 


during  admission  and  cooled  during  expansion  and  exhaust.    Let  //  be  this 
weight,  changing  by  a  quantity  of  heat,  n  c  d  T. 

—  n^r  d  T. 
mr 


T  T  T*  '    T. 

Integrating  both  sides  from  T0  to  T, 

-  CM  +  /to  J"  c  ^  =  ~  +  constant. 


-  M  + 


Taking  one  of  our  experiments  for  example  —  that  of  September  7,  for 
instance: 

M  =  0.2240  k.,  m0  =  0.1688  k.,  ml  =  0.1761  k. 
Cm  =  1.006096,  T0  =  414.85°,  2\  =  357.85°. 
r0  =  506.55  c.,  r,  =  547.10  c. 


0.2240  +  ^  =  0.42445,  u  =  0.20045,  and  the  heat  yielded  by  this  equivalent 
weight  of  water  is  //  (g0  —  qj  —  0.20045  (143.26  —  85.32)  =  11.61  c. 

Finally,  the  work  of  expansion  deduced  from  this  heat  yielded,  and 
the  difference  between  the  internal  heats  at  the  beginning  and  end  of 
expansion  is  A  F.,  =  Q  +  £70  —  C/i  =  11.61  +  1.66  =  13.27  c.,  while  the  value 
from  the  diagrams  is  14.31,  an  error  of  only  1.04  c.,  while  the  generic 
hypothesis  was  an  error  of  12.65  c. 

The  following  table  gives  the  value  of  the  work  of  expansion,  calcu- 
lated in  this  way,  and  also  from  the  diagrams,  with  their  difference.  The 
greatest  error  is  1.51  c.,  while  the  others  are  mostly  less  than  1  —  an  error 
of  less  than  1  per  cent,  of  the  total  heat  brought. 

TABLE  XI. 


,  a  ! 
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o 

§ 

> 

r 

* 

; 

j 

\ 

3 

i 

5 

4 

i 

3 

t-^ 

i 

X 

"ft 

8 

«! 

% 

t 

K 

•z 

•< 

( 

(J 

OQ 

£ 

OQ 

° 

Calculated  A  FA 

16.003 

U 

73 

Uf 

01 

7 

73 

13.27 

12.75 

6.78 

14.52 

Direct  .... 

....    16  520 

u 

ga 

15 

79 

•i 

"4 

14.31 

13.70 

7.22 

14.50 

Difference  

0.523 

0 

u 

1 

.78 

1 

.51 

1.04 

0.95 

0.44 

0.02 

We  have  shown  how  the  water  deposited  upon  the  surface  at  the  end 
of  the  stroke  is  partly  evaporated  during  exhaust,  how  it  carried  with  it  a 
certain  quantity  of  heat  Re,  which  we  have  called  the  cooling  by  the  con- 
denser. The  cylinder  in  these  conditions  works  as  a  boiler,  producing 
steam  which  goes  to  the  condenser  with  a  certain  quantity  of  water  en- 
trained with  it  the  amount  of  which  is  easily  determined.  The  condenser 


218 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


here  being  a  large  edition  of  that  used  in  determining  priming,  the 
method  of  calculation  is  identical;  that  for  September  7,  for  example,  is  as 
follows: 

Mean  back  pressure  1881  kgs.  per  square  metre: 

Temperature  t  corresponding  58.44°. 

q  =  58.57  c.     7.  =  624.32  c.     r  =  565.75  c. 

The  heat  found  in  the  condenser,  as  we  have  seen  above,  iy  122.77  c.,  the 
weight  of  fluid  per  stroke  is  0.2240  k.,  and  the  final  temperature  of  the 
water  is  30.42°,  whence  the  weight  of  entrained  water: 

0.2240  (A  —  30.42°)  —  122.77 
m  c  —   ---------- 

r 

_  0.2250  (624.32  —  30.42)  —  122.77 
565.75 


=  0.01815  k.    -  =  8.1  per  cent. 


The  following  table  shows  the  weight  of  water  and  its  proportion  of 
the  steam.  It  is  easy  to  see  that  it  depends  solely  on  the  proportion  of 
water  at  the  end  of  the  stroke. 


TABLE  XII. 


i 

06      !      oo 

i-l                  O* 

8    !    S 

t-' 

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00           :          <M 

oo 

o 

fc 

o 

1 

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CO 

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CO      |      OQ 

« 
O 

Carried  over  wt.  of  water  k. 
Per  cent.. 

0.0150 
4.6 

0.0349 
9.4 

0.02110.0087 
7-9       3.11 

0.01815 

8.1 

0.0280 
10.63 

0.0025 
1.1 

Non- 
condensing. 

General  Conclusions. — The  statement  of  the  method  used  in  experi- 
menting, the  checks  upon  the  results  reached,  which  accumulate,  shows 
us  with  what  exactness  the  data  have  been  obtained;  they  are  indisputable, 
as  well  as  the  results  derived  from  them,  such  as  the  temperatures,  heats 
of  evaporation,  densities,  etc.,  of  the  steam  which  proceeds  from  the 
pressures  following  certain  physical  laws,  which  are  mostly  expressed  by 
empirical  formulae  from  experiments,  and  are  contested  by  no  one  in  our 
day. 

We  find  ourselves  with  this  group  of  exact  data  in  the  presence  of  two 
theories  of  the  engine,  that  which  till  to-day  has  been  universally  re- 
ceived, the  generic  theory,  which  does  not  consider  the  properties  of  the 
bodies  and  fluid  which  are  under  the  influence  of  heat;  in  a  word  that 
which  considers  the  steam  as  working  in  a  non-conducting  cylinder.  The 
other,  the  theory  that  M.  Him  has  so  judiciously  called  "practical,"  hold- 
ing account  of  the  actions  which  take  place  between  the  steam  and  the 
surrounding  masses  of  metal.  This  latter  theory  could  only  be  established 
by  experiments.  It  is  the  study  of  the  working  engine,  and  each  condi- 
tion imposed  demands  a  new  experiment  and  a  new  analysis. 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  219 


One  easily  understands  that  it  is  convenient  to  construct  from  the  laws 
of  physics  a  theory  of  the  steam  engine  without  the  long  and  tedious  pro- 
cess of  experimenting  and  computing  which  we  have  shown,  and  this  is  a 
great  part  of  the  reason  that  for  so  long  we  have  had  the  generic  theory 
only.  We  are  far  from  contesting  its  utility,  as  it  often  points  out  the 
road  to  be  followed  in  seeking  for  the  truth ;  but  we  are  obliged  to  discard 
its  equations  when  we  wish  to  get  even  approximate  results. 

To  harmonize  the  data  and  derived  results,  for  they  are  only  the 
manifestations  of  a  single  cause,  the  action  of  'heat  on  steam  and  the 
metallic  masses  surrounding  it  while  doing  external  work,  has  naturally  led 
us  to  condemn  practically  the  generic  theory  of  the  steam  engine. 

Meanwhile  it  is  very  useful,  serving  as  a  guide  in  our  researches,  for  we 
have  been  led  by  it  to  make  this  study  of  the  densities  and  volumes  of  the 
steam.  We  have  had  to  give  up  the  hypothesis  of  leaks,  the  proportions 
were  so  variable;  but  it  became  evident  that  the  generic  theory  led  to 
errors  of  36  per  cent.,  for  the  weight  of  steam  given  by  the  product  of  the 
volume  and  density  led  us  to  the  discrepancy  and  to  seek  its  cause. 

In  a  non-conducting  cylinder  the  difference  of  internal  heat  at  begin- 
ning and  end  of  expansion,  U0 — U-^,  should  give  as  the  work  of  expansion 
AFA.  Our  researches  showed  us  that  heat  furnished  from  outside  from 
the  metal  which  had  stored  it  up  by  condensing  steam  during  admission, 
but  storing  up  more  than  was  needed  for  the  work  of  expansion,  the  ex- 
ternal radiation  and  the  change  of  internal  heat,  which  led  us  directly  to 
the  discovery  of  the  internal  radiation  or  cooling  due  the  condenser  Re, 
which  we  verified  by  the  heat  found  in  the  condenser,  another  form  of  the 
action  of  the  surfaces.  Finally,  when  we  wish,  by  the  aid  of  the  relation 

dQ=McdT  +  dmr  —   ^^  d  t  to  verify  the  work  of  expansion  AFA,  by 

supposing  it  in  a  non-conducting  cylinder,  we  arrive  at  absurdities  and 
impossibilities,  and  on  the  other  hand  the  natural  hypothesis  of  consider- 
ing a  part  of  the  mass  of  metal  as  water,  has  led  M.  Him  to  a  relation 
which  verifies  the  work  of  expansion  in  a  very  remarkable  manner.  To 
sum  up  all  of  our  analyses  shows  that  it  is  only  by  the  practical  theory 
that  we  can  render  an  exact  account  of  the  facts. 

DIRECT  PRACTICAL  RESULTS  OF  THESE  EXPERIMENTS. 

In  all  that  has  preceded  we  have  only  had  one  aim,  that  of  showing  the 
very  energetic  action  of  the  metallic  surfaces  inclosing  the  steam,  showing 
that  the  errors  found  in  the  results  of  the  ordinary  theories  of  steam  en- 
gines were  due  to  neglecting  their  influence. 

Each  of  our  readers  will  have  already  perceived  the  importance  of  this 
group  of  experimants  in  designing  engines.  Without  doubt  practice  has 
led  to  more  than  one  happy  idea,  for  example,  the  separate  condenser  and 
the  steam  jacket  of  Watt;  but  these  improvements,  to  be  valued  in  exact 
figures,  demanded  a  complete  analysis  of  the  engine,  such  as  we  have 
given,  for  it  is  only  then  that  the  results  cannot  be  gainsaid.  For  in  ou 


220  STEAM  USING;  07s",  STEAM  ENGINE  PRACTICE. 


day  we  find  some  engineers  affirming  that  it  is  possible  to  work  a  high- 
pressure  engine  as  economically  as  with  condensation;  and  the  utility  of 
steam  jackets  is  not  yet  put  beyond  doubt,  as  M.  Him  has  well  said  in  his 
"Analytical  and  Experimental  Exposition  of  the  Mechanical  Theory  of 
Heat:"  "I  have  already  said  that  the  effect  of  the  steam  jacket  has  been  al- 
ternately affirmed  and  denied  without  there  being  any  real  knowledge  of 
the  matter.  Some  say  the  jacket  has  no  useful  effect,  others,  that  it  gives 
40  per  cent,  more  work  with  the  same  steam.  It  is  easy  for  us  to  perceive 
the  origin  of  so  diverse  statements,  knowing  that  under  certain  circum- 
stances each  of  them  has  a  foundation.  The  essential  action  of  the  jacket 
consists  in  diminishing  the  quantity  Re  of  heat  that  the  steam  takes  from 
the  surface  to  the  condenser,  -and  in  augmenting  the  work  of  expansion 
AFd,  but  this  action  varies  with  the  engine  itself.  In  the  study  of  the  sin- 
gle cylinder  engine  we  found  that  in  diminishing  Re  and  increasing 
AFA  the  jacket  only  gave  little  heat  to  steam  during  expansion,  and  that 
the  greater  part  of  the  useful  heat  given  by  the  surface  came  from  the 
heat  stored  during  admission. 

"The  study  of  the  double  cylinder  'Woolf  engine  shows  us  on  the 
contrary  that  it  is  the  heat  given  by  the  jacket  which  increases  A  F{{. 
Before  such  striking  differences,  due  to  such  apparently  insignificant 
difference  of  details,  we  are  brought  to  recognize  that  a  single  cylinder 
un jacketed  engine  may  by  reason  of  details  better  utilize  the  heat  stored 
in  the  surface  during  admission  than  any  other.  It  is  not  impossible,  but 
even  probable,  that  the  relation  between  A  FA  and  Re  depends,  for  in- 
stance, upon  the  proportion  between  diameter  and  stroke,  or  the  total 
volume  to  the  volume  at  cut-off.  It  is  evident  that  the  jacket  will  give 
results  less  marked  upon  the  engine  which  works  best  without  it,  and 
better  when  A  Ftl  is  small  compared  with  Re.  In  a  word,  the  results  of  a 
steam  jacket  may  vary  within  10  to  25  per  cent." 

The  same  method  of  analysis  gives  the  economy  which  should  be 
realized  by  compression.  This  economy  stated  by  Zeuner  can  be  experi- 
mentally verified.  I  have  found  10  per  cent,  for  a  "  Woolf "  engine,  but  it  was 
only  by  following  all  the  transformations  of  steam  in  the  cylinders,  that  it 
was  possible  for  me  to  solve  this  problem  and  to  bring  a  first  experimental 
confirmation  to  the  fine  theorem  of  Zeuner. 

We  give,  then,  summing  up  in  a  last  table,  on  opposite  page,  the  re- 
sults of  our  eight  experiments,  believing  it  easier  to  follow  the  problems 
with  their  experimental  conclusions,  for  a  glance  will  establish  the 
relations. 

The  first  anomaly  that  strikes  us  is  that  the  consumption  in  experi- 
ments made  in  1873  is  different  from  those  of  1875  under  the  same  condi- 
tions. The  explanation  is  that  the  engine  had  a  new  cylinder  with  larger 
ports,  and  the  exhaust  was  considerably  earlier.  Thus  a  modification 
which  in  the  limits  made  would  seem  unimportant,  has  produced  an 
improvement  of  9  per  cent.  This  proves  that  nothing  should  be  neglected 
in  designing  an  engine. 

We  shall  be  forgiven  if  we  speak'again  upon  the  question  of  leakage, 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


221 


the  practical  importance  of  the  subject  is  reason  for  returning  to  it,  not 
for  this  engine,  which  we  showed  to  be  sufficiently  tight,  but  as  general 
conditions  bearing  upon  the  construction  of  engines. 

TABLE  XIIL 


= 
= 

s; 


e*n 

-  0; 

5» 

OD 


i, 

Nov.  18,  1873,  steam  at  231°  C 44.2449144.36    7.688 

Nov.  28,  1878,  saturated 43-7773  136.4610.026 


52    ° 
I|    I 

ss    s 


12.00 
25.20 


Aug.  26,  1875,  steam  at  215°  C 5  4.1415  135.77    7.002!  17.05 


Aug.  27, 
Sept.  ,, 

"    29, 
Oct.  28, 


223C  C.  (throttled) ;  2  2.3070  125.17    8.199    13.20 

195°  C !  73.9128113.08    7.126;  21.38 

saturated 73.8339107-81    8.915'  35.19 

steam  at  220°  C.  (throttled) 21.7458    99.53    8.227    15.85 

steam  at  220°  C.  (non-condensing) 43.4333    78-3012.3151 ! 


7.8 
15.6 

9.7 
10.5 
12.43 
21.76 
14.21 


We  have  seen  that  it  was  impossible  to  attribute  to  leakage  the  steam 
condensed  during  admission,  and  we  had  to  conclude  that  the  engine 
piston  was  tight,  the  packing  of  the  most  simple  kind — two  cast  iron  rings 
turned  larger  than  the  cylinder,  cut  and  sprung  in,  the  two  ends  coming 
together.  Some  builders  think  this  lacks  elasticity;  for  cylinders  of  large 
diameter,  over  one  metre,  they  prefer  to  have  segments  set  out  with 
springs.  Whichever  are  used  we  can  always  have  tight  packings  when 
well  set  up  and  working  vertically. 

It  is  easy  to  see  that  it  is  the  vertical  disposition  which  keeps  the  pack- 
ing in  order,  for  it  places  the  segments  in  the  most  favorable  conditions 
possible.  Besting  on  the  follower,  they  are  in  a  manner  equilibrated  dur- 
ing motion  in  the  same  condition  at  all  points  of  the  stroke,  with  nothing 
to  counteract  the  lateral  pressure  they  exert  on  the  cylinder.  They  can  be 
set  with  little  tension  so  as  to  keep  them  tight  with  the  least  possible 
friction.  One  should  not  hesitate  for  large  power  with  room  enough, 
almost  always  to  be  had  with  stationary  engines,  to  give  the  preference  to 
vertical  engines. 

But  if  the  problem  of  light  pistpns  has  been  solved  for  vertical  en- 
gines, the  results  with  others  is  far  from  being  satisfactory;  they  nearly 
always  leak,  if  not  at  first,  after  a  short  time;  and  it  could  not  be  otherwise 
from  the  cylinder  wearing  oval  from  the  weight,  and  the  segments  not 
being  carried  by  the  piston. 

They  have  tried  to  remedy  this  defect,  more  or  less  happily  in  many 
cases,  by  a  steam  packing;  but  this  is  difficult  to  adjust  and  gives  the 
greatest  wear  at  the  ends  of  the  cylinder.  Sometimes  the  leaks  may  be 
neglected,  but  we  usually  find  the  horizontal  piston  in  default. 


222  STEAM  USING;  OS,  STEAM  ENGINE  PRACTICE. 

In  the  marine  service  they  have  obtained  very  good  results  with  rings 
of  "anti-friction"  metal,  but  these  are  often  changed,  and  watched  with 
great  care.  In  any  case,  it  is  indispensable  to  set  the  piston  in  such  a 
manner  that  its  weight  shall  not  be  carried  by  the  ring;  to  give  it  a  rod 
with  rigidity  enough  to  keep  it  from  flexures  and  to  carry  it  on  guides  at 
each  end.  Unfortunately  this  gives  a  double  extent  of  cooling  surface  for 
the  rod  alternately  exposed  to  steam  and  air. 

We  do  not  insist  upon  the  economy  of  the  use  of  superheated  steam, 
for  the  experiments  made  in  1865  by  the  Committee  of  the  Society  have 
sufficiently  proved  that.  And  we  only  verify  the  results  of  that  time. 
There  is  23  per  cent,  for  the  experiments  of  November  18  and  28,  and  20 
per  cent,  for  those  of  September  7  and  8. 

But  it  may  be  useful  to  rapidly  enumerate  the  evils  which  are  said  to 
be  involved  with  its  use;  to  examine  its  mode  of  action  which  Him  has 
so  well  described  in  his  new  work  on  thermodynamics.  After  having 
analyzed  the  effect  of  the  jacket,  he  shows  that  bringing  into  the  interior 
of  the  cylinder  a  greater  quantity  of  heat  than  comes  \v  ith  the  saturated 
steam  is  more  energetic  than  surrounding  the  cylinder  by  a  jacket.  For 
the  heat  brought  by  the  jacket,  steam  condensing  on  the  outside  of  the 
cylinder  has  to  cross  the  metal  before  it  can  modify  the  condensation 
during  admission,  it  can  not  do  this  rapidly  enough,  and  we  find  conden- 
sations even  in  the  small  cylinder  of  compound  "Woolf"  engines,  which 
are  open  to  the  boiler  nearly  full  stroke;  for  the  heat,  and  above  all,  the 
superheat,  the  steam  brings  directly  into  contact  with  the  surface,  which 
has  been  cooled,  and  we  have  seen  in  one  of  our  experiments  the  expan- 
sion commences  with  superheated  steam.  Another  precious  advantage,  it 
furnishes  heat  without  condensing,  giving  dryer  steam  at  the  end  of  the 
stroke,  diminishing  by  that  the  internal  radiation  to  the  condenser  Re. 
It  does  not,  as  the  jacket  does,  furnish  its  heat  at  the  wrong  time  when 
open  to  the  exhaust.  When  this  commences  the  surfaces  of  cylinders 
using  superheated  steam  are  at  temperatures  little  higher  than  that  corres- 
ponding to  the  terminal  pressure,  the  heat  lost  when  the  steam  escapes  is 
then  small,  while  the  jacket  steam  at  the  boiler  temperature  accelerates 
the  evaporation  of  the  water  which  covers  the  surface,  sending  to  the 
condenser  the  most  heat  when  it  should  send  the  least  to  make  Re  a 
minimum. 

As  for  the  objection,  raised  against  superheating,  we  shall  say  with 
Him,  that  "Setting  aside  some  excellent  but  purely  theoretical  works  we 
stop  before  the  critical  judgment  of  those  who  to-day  call  themselves 
'practical.'  We  discard  all  opinions  resting  upon  anything  but  facts  and 
the  spirit  of  impartial  investigation."  We  can  only  discuss  those  among 
them  which  appear  to  have  a  real  basis.  They  always  say  that  superheat- 
ing burns  the  oil  which  should  lubricate  the  piston  and  rod  packings. 
Practice  has  shown  that  this  is  not  true  up  to  230°  C.  (44G°  F.),  and  that  it 
is  not  necessary  to  renew  the  oil  more  frequently  than  with  common 
steam;  that  the  surfaces  of  the  cylinder  are  kept  in  as  good  condition 
without  cutting,  but  we  know  that  the  steam  in  the  cylinder  is  still  satu- 


THE  ALSA  TIAN  EXPERT)!!:  A  7  >,  K  T<  .  223 

rated,  only  dryer.    Even  if  brought  in  at  230°  C.,  it  is  impossible  to  sustain 
that  it  will  burn  the  oil  and  destroy  the  cylinder  in  which  it  is  worked. 

There  are  three  questions  of  the  highest  interest  long  discussed  in 
many  theoretical  works  which  can  only  be  answered  by  experiments,  and 
this  solution  is  so  natural  that  one  is  astonished  to  see  it  so  long  unem- 
ployed: 1.  The  limits  of  economic  expansion.  2.  The  effects  of  throt- 
tling. 3.  The  use  of  the  condenser. 

Influence  of  Expansion. — The  universal  opinion  to-day  is  that  the 
greater  the  expansion  the  greater  the  economy  of  fuel,  and  one  is  brought 
naturally  to  continue  it  to  the  pressure  of  exhaust,  and  the  dimensions 
given  the  cylinder  are  only  limited  thereby.  But  as  M.  Hirn  has  remarked 
in  his  book,  if  we  push  expansion  too  far  we  have  less  upon  the  piston 
than  is  required  to  move  the  engine  and  overcome  friction— we  then  do  no 
good.  It  is  a  lower  limit  which  should  never  be  passed,  and  if  we  wish  to 
know  how  far  we  can  reduce  the  initial  volume  compared  with  the  final 
volume  with  a  constant  consumption  our  experiments  give  us  the  neces- 
sary figures  for  this  comparison.  For  a  long  time  the  question  has  been 
treated  differently  in  purely  theoretical  works,  and  we  shall  see  to  what 
errors  the  generic  theory  has  led,  such  as  calculating  from  inexact  experi- 
mental data  the  law  of  expansion,  for  this  law  is  only  an  empirical  state- 
ment of  the  exchanges  of  heat  during  expansion,  changes  which  vary 
with  the  conditions  imposed  upon  the  engine,  and  of  which  analyses  such 
as  we  have  given  can  alone  define  the  value  and  employment. 

We  have  operated  with  an  introduction  from  £  to  \  the  limits  of  valve 
gear.  The  experiment  with  cut-off  £,  it  is  true,  was  made  with  engine  throt- 
tled; but  we  will  justify  this  later,  treating  of  the  question  of  throttling,  and 
we  have  the  results  of  a  lower  pressure  than  with  the  other  experiments. 

Taking  the  figures  from  the  preceding  table,  with  superheated  steam 
we  have  1  per  cent,  in  favor  of  five  expansions  over  seven  expansions. 
Exact  values:  Introduction  0.1628,  consumption  7.126  k.;  introduction 
0.2570,  consumption,  7.002.  If  we  correct  by  9  per  cent,  the  experiments 
of  November  18  and  28,  1883,  for  the  reasons  given  above,  we  see  that  the 
consumption  of  November  18,  6.996  k.,  is  very  close  to  those  cited.  This 
constancy  of  consumption  holds  also  with  saturated  steam  as  well  as  with 
superheated,  a  more  remarkable  circumstance.  Thus  correcting,  the  ex- 
periment of  November  28,  1873,  9.024  k.,  and  for  September  8,  1885,  8.915 
k.  per  I.  H.  P.,  figures  within  1.2  per  cent.  Such  are  the  results  of  exper- 
ience. Let  us  see,  if  possible  without  a  full  analysis,  which  is  preferable. 

Between  the  experiments  of  7th  September  and  26th  August,  1875,  the 
work  varied  from  113  to  136  H.  P.;  the  water  at  the  commencement  of 
expansion  from  24.6  to  0.8  per  cent.  But  it  is  objected,  on  the  7th  Sep- 
tember the  superheating  is  20°  less.  This  is  only  2.24  c.  loss,  or  2'24  =1.4 

151.5 

per  cent.,  almost  exactly  the  difference  in  consumption. 
7.126  —  7.002 


7.126 


=  1.7  per  cent. 


224  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

Thus,  while  using  superheated  steam,  we  have  in  the  one  case  the 
steam  dry,  in  the  other  with  one-fourth  water  condensed  on  the  surfaces. 
All  the  functions  of  the  engines  are  completely  changed  in  these  two  ex- 
periments. On  August  26  the  internal  heat  U  of  the  steam  diminishes 
during  the  expansion,  doing  the  work  thereof,  and  as  the  surfaces  have 
only  absorbed  9  c.,  during  admission,  a  part  also  is  radiated  to  the  con- 
denser in  Re.  While  on  September  7  the  internal  heat  U  of  the  steam  is 
nearly  constant  during  expansion  within  1.66  c.,  it  is  the  surface  which 
does  the  work  of  expansion,  Re  having  received  33.95  c.  As  we  see  a  rad- 
ical difference  in  the  mode  of  transmitting  heat,  and  in  each  experiment 
the  same  weight  of  steam  has  produced  the  same  work,  the  final  result 
being  the  same.  In  the  presence  of  such  facts,  how  can  one  say,  from  the 
diagram  only,  for  example,  how  much  expansion  should  be  given?  To 
establish  this,  the  verified  data  are  needed  which  we  have  already  used. 

We  find  that  when  we  have  carried  the  introduction  to  half  stroke,  but 
throttling  also  to  give  125  H.  P.  for  one  and  99  H.  P.  for  the  other  experi- 
ment, that  for  each  case  the  consumption  is  not  affected  by  the  throttling, 
which  was  different  in  the  two  cases.  This  permits  us  to  compare  these 
experiments  with  those  cutting  off  at  |  and  f  stroke,  finding  a  saving  by 

O    -J  QQ   7    AAQ 

the  latter  of  _      -L^  =  14.59  per  cent,  by  the  greater  expansion. 
8.190 

On  the  other  hand,  we  see  that  as  the  work  was  diminished  the  pro- 
portion of  water  at  the  end  of  the  stroke  was  increased,  as  also  the  dead 
loss  Re.  By  cutting  off  less  than  %  we  should  find  a  point  where  Re  would 
change  the  law  and  the  consumption  would  increase,  but,  unfortunately, 
the  valve  gear  would  not  admit  of  such  a  trial. 

We  have  referred  to  the  indicated  work,  but  this  is  lessened  by  friction 
for  the  useful  work,  and  the  friction  is  not  proportioned  to  the  indicated 
work.  This  limits  the  cut  off  to  between  |  and  1  for  the  best  results  for 
the  single  cylinder  engine. 

Effects  of  Throttling. — The  question  of  restricting  the  area  of  the 
orifices  of  admission  has  been  less  often  agitated  than  the  cut  off,  and 
like  that  can  only  be  resolved  by  direct  experiments,  fully  analyzed. 
Before  stating  the  results  we  have  obtained,  we  will  review  the  opinions 
put  forward.  Some  engineers,  basing  on  the  proposition  that  dry  steam 
falling  in  pressure  without  doing  external  work  becomes  superheated, 
have  asserted  that  throttling  was  beneficial  by  evaporating  the  water 
entrained  with  the  steam.  But  if  they  look  at  the  second  part  of  the 
proposition  "without  doing  external  work,"  they  must  admit  that  the 
amount  of  heat  wrought  per  unit  of  weight  is  the  same  in  either  case. 

Others,  considering  only  the  loss  of  work  resulting,  condemn  entirely 
all  methods  of  regulation  based  on  the  throttle  as  essentially  defective,  pro- 
scribing all  governor  throttles.  They  have  generally  attributed  the 
economy  that  they  believed  to  exist  in  the  Corliss  engines,  or  others  of  the 
class,  to  the  rapid  introduction  of  steam  at  nearly  the  boiler  pressure. 

We  should  attribute  this  radical  difference  of  opinion  to  the  conditions 
in  the  engines  observed.  We  have  seen  that  in  certain  limits  of  expan- 


THE  A LSA  TIAN  EXPERIMENTS,  ETC,  225 


sion  the  consumption  is  constant,  or  is  increased.  If  we  wish  light  work 
we  may  compare  £  cut  off  with  £  cut  off,  and  should  not  be  astonished  at 
a  difference  of  14  per  cent,  between  those  of  August  26  and  September  7 
with  £  and  \  cut-off,  and  those  of  August  27  and  September  29  with  £ 
throttle. 

To  compare,  we  should  not  take  the  basis  of  work  done,  but  the  cut- 
off, and  the  two  experiments  at  half  stroke,  with  the  valve  more  or  less 
closed. 

The  pressure,  on  August  27,  of  steam  at  223°  C.  was  brought  to  2.  307  k.  at 
cut-off,  and  on  September  29,  with  a  temperature  of  220°  C.,  to  1.7458  k.,  a 
difference  of  0.5612  k.  more  than  half  an  atmosphere,  and  the  consumption 


was  altered    ':^          =  o.3  per  cent.    The  increase  is  then  due  to  the 

8.227 

less  expansion,  as  we  have  seen. 

But  here,  contrary  to  what  was  found  with  different  expansions,  the 
percentage  of  water  is  almost  the  same  —  1.5,  or  slight  superheating,  and 
2.52  per  cent,  at  the  beginning  and  13.02  and  15.85  per  cent,  at  the  end  of 
expansion,  while  the  internal  heat  has  decreased  20.52  c.  and  16.82  c.  In 
wide  enough  limits,  as  we  see,  the  throttle  has  no  influence  upon  the  con- 
sumption. 

Effect  of  the  Condenser.  —  As  we  have  said,  resting  upon  facts  from 
which  the  following  proposition  is  derived,  that  a  vapor  introduced  into 
a  reservoir  with  constant  volume,  of  which  the  surfaces  are  not  every- 
where of  the  same  temperature,  its  final  pressure  depends  upon  the 
lowest  temperature,  that  Watt  deduced  for  his  condenser. 

The  figures  that  we  have  show  an  economy  of  43  per  cent,  by  the  con- 
denser over  exhaust  to  the  air,  a  result  needing  little  comment. 

Let  us  see,  however,  as  we  have  done,  how  this  effects  the  changes 
of  heat. 

At  the  cut-off  we  have  12  per  cent,  condensed  and  29.4  c.  stored  heat, 
the  work  of  expansion  requiring  only  14.5  c.,  and  Re  is  zero,  as  also  the 
proportion  of  final  water.  The  excess  from  the  surfaces  has  increased 
the  internal  heat  from  163.72  to  177.97  c.  We  see  that  the  loss  Re  exists 
in  a  different  form,  the  exhaust  carrying  off  an  excess  of  14.24  c.  to  the 
air,  as  an  increase  in  its  internal  heat,  and  we  have  lost  work  by  the  in- 
crease of  back  pressure. 

It  is  not  enough  that  Re  should  be  zero,  as  we  have  said,  but  the 
internal  heat  should  not  increase  to  put  the  engine  in  the  best  condition, 
and  there  should  be  no  lost  work,  or  the  best  vacuum  should  be  obtained. 
This  imposes  the  following  condition  —  the  surfaces  should  absorb  only 
the  work  of  expansion. 

Although  all  our  study  has  shown  us  how  little  freedom  we  have  in 
imposing  conditions  upon  the  action  of  the  surfaces,  we  believe,  resting 
upon  the  experiment  of  August  26,  cut  off  £,  that  by  the  use  of  super- 
heated steam  and  a  jacket,  the  loss  of  internal  heat  would  have  been 
reduced  from  26.05  c.,  and  with  dry  steam  at  the  end  of  the  stroke  dimin- 


226  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 

ished  Re.,  but  the  jacket  should  be  fed  by  a  separate  supply  pipe,  in  order 
not  to  cool  too  much  the  working  steam. 

There  only  remains  for  us  to  examine  what  proportion  of  heat  given 
has  been  utilized  to  finish  these  practical  deductions. 

When  one  measures  the  efficiency  of  an  hydraulic  motor,  one  divides 
the  power  utilized  by  that  furnished,  but  for  heat  engines  this  is  not  the 
case. 

Whatever  be  the  body  used,  in  a  heat  engine  of  maximum  efficiency, 
the  efficiency  depends  upon  the  difference  of  temperatures  between  which 
it  works,  divided  by  the  absolute  temperature  of  the  source  of  heat.  In 
these  unrealizable  conditions  we  should  get  249  H.  P.  for  100  calories,  as 
shown  by  Hirn.  The  best  of  our  experiments  give  135.77  H.  P.  for 

172.79  c.,  or  75.8  H.  P.  for  100  calories  ;  7®^  =  31.5  per  cent. 

Av9 

We  see  how  far  we  are  from  the  theoretic  effect,  and  while  stating  that 
it  never  can  be  reached,  we  should  hope  for  an  improvement  over  what 
is  practically  30  per  cent. 

To  sum  up,  thanks  to  the  numerous  checks  which  the  method  employed 
permits,  we  have  established  the  considerable  influence  of  the  action  of 
the  internal  surfaces  upon  the  action  of  steam  in  engine -cylinders,  and 
have  shown  how,  by  employing  superheated  steam  without  prejudice  to 
jackets,  a  considerable  loss  may  be  brought  to  a  minimum,  the  cooling 
due  the  condenser  Re.,  and  within  what  limits  it  is  judicious  to  confine 
expansion. 

Such  are  the  results  of  the  series  of  experiments  carried  out  under 
the  direction  of  M.  Hirn,  and  our  readers  can  judge  of  their  great  im- 
portance.* 

EXPERIMENTAL  STUDY  COMPARING  THE  INFLUENCE  OF  EXPANSION  IN 
SIMPLE  AND  COMPOUND  ENGINES. — A  PAPER  BEAD  BEFORE  THE  IN- 
DUSTRIAL SOCIETY  OF  MULHOUSE,  DECEMBER  30,  1878,  BY  M.  0.  HAL- 

LAUER.f 

The  comparison  of  the  many  experiments  made  upon  "  Woolf "  engines, 
and  the  engine  of  M.  Hirn,  with  superheated  steam,  led  me  to  a  principle 
which  has  been  confirmed  by  th,e  analysis  of  the  compound  engines  in 
use  in  the  French  navy .  I  had  stated  the  conclusion  in  a  paper  presented 
to  the  Society  on  the  30th  January,  1878: 

One  can  always  construct  a  single  cylinder  vertical- beam  engine,  steam 
jacketed  with  four  valves,  which  shall  be  at  least  as  economical  as  the  verti- 
cal "  Woolf"  beam  engine,  for  expansions  from  4  to  7,  if  the  clearance  does  not 
exceed  1  per  cent,  of  the  cylinder  volume. 

This  conclusion  is  based  upon  the  total  work  of  the  engine,  supposing 

*These  papers  are  given  in  the  direct  reverse  of  the  order  of  their  original  publica- 
tion, but  perhaps  not  of  their  value.— C.  A. S. 

tM.  Keller's  summary  of  the  following  experiments  was  given  in  the  opening  section 
of  this  Chapter.— C.  A.  S. 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  227 

a  perfect  vacuum — in  a  word,  we  consider  the  intrinsic  work  of  the  steam 
itself. 

In  this  memoir  I  have  had  occasion  to  examine  the  various  considera- 
tions which  serve  to  establish  the  superiority  of  the  "Woolf "  system,  outside 
of  the  experimental  domain. 

These  same  considerations  I  have  again  found  developed  under  a  form 
nearly  identical  but  very  marked  in  two  works,  concerning  the  "Woolf" 
engines,  with  expansion  in  the  small  cylinder.  The  authors  there  sum  up 
what  is  generally  admitted  in  favor  of  the  "Woolf"  system,  which  I  will 
cite  literally  to  allow  the  reader  to  appreciate  the  utility  of  my  previous 
paper. 

The  first  of  these  works  was  published  at  Kouen  by  MM.  Thomas  & 
Powell,  engineers.  It  contains  the  experiments  made  in  June,  1876,  by 
M.  H.  Roland,  Engineer  of  the  Norman  Association  of  Steam  Users,  and  it 
opens  thus: 

"Double  cylinder  engines,  in  which  the  steam  acts  successively,  pro- 
duce motive  force  most  economically  when  well  constructed  and  managed. 
The  advantage  is  because  the  small  cylinder  is  only  in  communication 
with  the  condenser  for  a  moment,  the  large  cylinder  only  being  more  con- 
tinually so,  and  the  first  action  is  to  withdraw  a  portion  of  the  force 
produced  from  the  cooling  action  of  the  condenser  and  the  internal  con- 
densation which  is  the  immediate  consequence. 

"The  steam  arrives  at  the  large  cylinder  partly  expanded,  and  conse- 
quently at  a  lower  temperature  than  that  in  the  jacket,  and  is  easier 
warmed  and  the  condensation  notably  lessened. 

"The  employment  of  two  cylinders  permits  us  to  carry  the  principle 
of  expansion  to  its  extreme  limit  with  the  best  economic  conditions,  the 
force  generated  is  divided,  the  efforts  better  carried  and  the  differences  of 
power  between  beginning  and  end  of  stroke  are  less  than  in  a  single 
cylinder  engine;  working  with  the  same  admissions  there  results  a 
smoother  operation.  Because  of  the  vertical  cylinders  and  perfect  equi- 
librium of  the  pieces  attached  to  the  beam  the  frictions  are  reduced  and 
the  useful  effect  is  very  high.  It  is  to  these  qualities  that  the  long  life  of 
these  engines  is  to  be  attributed.  We  can  cite  some  which  have  worked 
thirty  years  and  which,  after  modifications  with  comparatively  little  cost, 
are  in  perfect  order  for  work  and  consumption. 

"The  addition  of  a  'Correy  Governor  Expansion  Gear,'  assures  to  the 
engines  which  are  furnished  with  it  a  perfect  uniformity  of  speed  and 
economic  utilization  under  all  loads." 

The  second  work,  published  in  1878,  in  the  Annual  of  the  Society  of 
Graduates  of  the  Schools  of  Arts  and  Trades,  under  the  title  of  "Notes 
Upon  Double- Cylinder  Engines,"  contains  the  results  of  experiments  made 
by  M.  Que'm,  upon  engines  at  St.  Eemy,  constructed  by  MM.  Powell. 

"Among  the  different  types  of  engines  actually  in  use,"  says  M.  Quern, 
"the  'Woolf,'  with  two  cylinders  jacketed,  in  which  the  steam  acts  suc- 
cessively, is  that  which  gives  the  best  economy  in  production  of  motive 
force. 


228  STEAM  USING;  OS,  STEAM  ENGINE  PRACTICE. 


"In  these  engines  the  steam  acts  first  with  or  without  expansion  in  the 
small  cylinder,  then  with  expansion  in  the  large  cylinder.  The  latter  only 
is  in  communication  with  the  condenser.  By  this  arrangement  a  portion 
of  the  force  produced  escapes  the  cooling  action  of  the  condenser  and  the 
internal  cylinder  condensation. 

"Finally,  because  the  jackets  are  connected  with  the  boilers,  the  ex- 
panding steam  in  the  large  cylinder  is  at  a  temperature  below  that  of  the 
jacket,  and  is  warmed  thereby,  and  the  cylinder  condensation  is  notably 
lessened. 

"The  employment  of  two  cylinders  permits  the  best  realization  of  ex- 
pansion, which  in  these  'Woolf  engines  can  be  carried  to  its  limit. 

"The  difference  of  force  between  the  beginning  and  end  of  the  stroke 
is  less  in  double  than  in  single  cylinder  engines;  there  results  smoother 
working. 

"Because  of  the  lesser  difference  of  pressures  there  are  less  risks  of 
breaking. 

"Finally,  leakage  of  steam  by  the  admission  valve  is  less  prejudicial 
than  in  single  cylinder  engines. 

"In  'Woolf  beam  engines  the  balancing  of  weights  reduces  the  fric- 
tion, and  the  useful  effect  is  consequently  high. 

"We  have  said  that  their  principle  assures  to  the  'Woolf  engines  regu- 
larity of  speed.  That  is  true,  but  the  regulators  which  have  been  applied 
for  the  purpose  of  rendering  the  speed  uniform  under  variable  loads  have 
been  far  from  perfect  or  from  giving  the  desired  results. 

"The  apparatus,  long  employed  upon  single -cylinder  engines,  is  the 
conical  governor  and  butterfly  throttle. 

"Not  only  is  the  governor  throttle  unsatisfactory  in  point  of  speed,  but 
its  operation  is  bad  from  the  standpoint  of  economy. 

"In  effect  it  operates  upon  the  steampipe,  opening  or  closing  a  pas- 
sage. 

"There  results  a  throttling  which  produces  an  expansion  not  only 
useless  but  prejudicial  in  the  pipe  and  steam  chest,  consequently  a  low- 
ering of  initial  pressure,  which  loss  of  force  augments  the  consumption  of 
fuel. 

"It  had  been  desirable  to  put  on  'Woolf  beam  engines  a  variable  expan- 
sion gear  which  should  be  easily  put  on,  which  should  give  these  engines 
great  regularity  of  speed,  avoid  the  evils  of  throttling,  and  obtain  a 
greater  expansion. 

"Valves  with  lap  which  had  been  applied  for  some  years  to  these  en- 
gines were  a  great  improvement,  but  the  expansion  was  fixed  and  was  not 
sufficient  in  most  cases,  and  moreover  the  throttle  was  retained. 

"Correy's  variable  gear  permits  us  to  add  to  the  advantages  of  the 
'Woolf  engines  the  removal  of  the  throttle,  retaining  an  economic  use  of 
steam  under  all  loads. " 

Of  all  the  foregoing  considerations  one  only  is  not  to  be  contested;  it 
is  as  MM.  Powell  say,  that  the  efforts  are  better  distributed  and  the  differ- 
ences of  force  between  the  beginning  and  end  of  the  stroke  are  less  than 


THE  ALSATIAN  EXPERIMENTS,  ETC.  229 

in  single- cylinder  engines,  and  the  movement  smoother.  But  it  should 
not  be  concluded  from  this  long- known  fact  that  the  useful  effect  of 
double-cylinder  engines  is  high  and  economical.  The  brake  experiments 
made  by  the  Mechanical  Committee  of  the  Industrial  Society  of  Mulhouse 
have  proved  that  the  friction  of  the  engines  absorbs  more  power  in  'Woolf 
engines  than  in  single -cylinder  engines. 

I  have  already  shown  in  my  paper  of  1878  what  economy  can  be  real- 
ized by  expansion  in  a  separate  cylinder.  But  the  principle  which  I  have 
stated  has  raised  so  many  contradictions  that  our  mechanical  committee 
has  deemed  it  prudent  to  hold  itself  in  reserve  when  it  states  in  these 
terms  at  the  close  of  my  work:  "Many  times  already  the  committee  has 
given  its  entire  approbation  to  the  fruitful  experimental  method  followed 
by  our  colleague,  and  recommends  to  the  attention  of  all  engineers  the 
results  of  the  experiments  contained  in  this  work,  results  which  appear  to 
him  unattackable.  On  the  contrary,  the  committee  believes  it  should  be 
less  positive  in  the  conclusions  of  the  author;  it  desires  to  see  them  con- 
firmed by  a  great  number  of  cases,  and  above  all  by  varied  experience  in 
the  widest  field."  I  believed  it  useful  to  renew  this  question  with  new 
data,  and  more,  I  have  added  the  study  of  an  expansion,  more  or  less,  in 
the  small  cylinder  of  the  'Woolf  engine. 

INFLUENCE   OF  EXPANSION  IN  "  WOOLF"  ENGINES. 

Can  there  be  a  notable  economy  in  cutting  off  in  the  small  cylinder  of 
a  "Woolf"  engine  and  expanding,  for  example,  28  times?  Such  is  the  first 
question  which  we  shall  attempt,  for  it  is  necessary  to  verify  the  con- 
sumption reported  in  each  of  the  experiments  which  we  shall  cite,  and 
this  defines  the  degree  of  confidence  which  we  shall  give  them. 

It  may  be  useful  to  recall  to  our  readers,  in  the  interest  of  the  ques- 
tion which  occupies  us,  the  passage  in  my  memoir  of  1878,  bearing  upon 
this  question  of  the  influence  of  expansion. 

The  three  engines  where  the  expansion  was  effected  in  a  separate 
cylinder  are  ranged  in  order  of  their  consumption  per  total  horse-power 
per  hour.* 

Vertical  Woolf  engine,  7.112  k.  (15.4  Ibs.);  horizontal  "Woolf"  engine, 
7.290  k.  (15.9  Ibs.);  compound  engine,  7,510  k.  (16.4  Ibs.).  But  this  is  also 
the  order  of  expansion:  Vertical  "Woolf,"  7  times;  horizontal  "Woolf,"  6 
times;  compound,  5  times. 

The  fact  that  the  consumption  per  total  horse-power  per  hour  was 
increased  by  changing  the  cut-off  from  f  to  £  was  also  found  with  the 
single  cylinder  engine  using  superheated  steam.  But  we  should  observe 
that  the  reduction  of  the  volume  at  cut-off  causes  a  reduction  of  useful 
work  by  the  engine,  and  at  the  same  time  a  relative  increase  in  the  back 
pressure  work.  In  the  engine  with  superheating,  and  above  all  in  the 
"Woolf"  engines,  this  increase  of  back  pressure  work  not  only  annuls  the 

*The  French  weights  are  for  a  Cheval  de  Vapeur,  translated  H.  P.  English  equiva- 
lents are  in  parentheses.— C.  A.  8. 


230  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

economy  of  a  prolonged  expansion,  but  even  causes  a  greater  expense. 
Also  the  back  pressure  work  passing  from  17  to  20  per  cent,  destroys  the 
economy  of  the  vertical  "Woolf,"  when  the  regulating  valve  lowering  the 
pressure  reduces  the  work  from  347  to  267  horse-power. 

The  documents  which  will  serve  us  in  the  study  of  expansion  are: 

1.  Experiments  made  in  1877  at  Munster  upon  a  "Woolf"  beam  engine, 
built  by  the  firm  of  Andre'  Koechlin  (really  the  Alsatian  Society  of  Mechan- 
ical Constructions),  and  figuring  in  my  memoir  of  1878. 

2.  Brake  Experiments  by  the  Mechanical  Committee  of  the  Industrial 
Society  in  1876  upon  a  horizontal  *"Woolf "  by  the  same  builder,  and  given 
in  the  Bulletins,  July,  1877. 

3.  Experiments  made  in  1877  by  the  Alsatian  Association  of  Steam 
Users  upon  a  vertical  "Woolf"  engine  at  Malmerspach  having  a  variable  cut- 
off in  the  small  cylinder,  by  the  same  builder. 

4.  Experiments  made  upon  "Woolf"  beam  engines  with  expansion  in 
the  small  cylinder,  built  by  MM.  Thomas  and  T.  Powell,  of  Kouen,  and 
tried,  one  in  1877  at  St.  Kemy  upon  Arne  by  M.  Quern,  and  the  other,  in 
1876,  by  the  Norman  Association  of  Steam  Users,  this  latter  running  the 
shops  of  MM.  Fauquet-Lemaitre  at  Bolbec.     The  direct  results  of  these 
experiments  upon  the  Powell  engines  and  that  at  Malmerspach  have  been 
given  me  by  M.  H.  Walther-Meunier,  Engineer  of  the  Alsatian  Association 
of  Steam  Users.    I  have  checked  and  analyzed  them.     The  analysis  of  the 
other  experiments  is  given  in  my  preceding  paper,  as  I  have  already 
said:  Andre'  Koechlin,  "Woolf"  Beam  Engine  working  at  Munster,  variable 
power  by  throttle  expansion,  7  times. 

CHECK  UPON  CONSUMPTION,  GAUGED  DIRECTLY,  TAKING  AS  A  BASE  THE 
HEAT  GAINED  BY  THE  COLD  WATER  INJECTED  TO  THE  CONDENSER. f 

I. — Forces  des  Chevauxs,  translated  horse-power,  I.  H.P.,  347.16;  revo- 
lutions per  minute,  25.25;  net  H.  P.  on  brake,  303.16;  mechanical  effi- 
ciency, 87.3  per  cent.;  proportion  of  back  pressure  work  to  total  work, 
17.  43  per  cent.;  back  pressure  on  large  piston,  0.293  k.  (4.2  Ibs.  per  sq.  in.) 
(Boiler  pressure,  67  Ibs.  above  atmosphere.) 

Per  Single  Stroke. 

Heat  brought  by  dry  saturated  steam 0.9123  k.  x  654.03  c.  =  597.19  c. 

"  "          "  water  entrained 0.0290  k.  x  157.47  c.  =     4.44  c. 

"  steam  condensed  in  jackets  0.0884k.  x  496.56  c.  =    43.89  c. 

Total  heat  brought  to  engine 645.52  c. 

Heat  kept  by  the  steam  leaving  condenser 0.9413  x  34.25  =    —32.24  c. 

Qo 613.28  c. 

*In  the  table  given,  on  page  191  this  engine  is  headed  as  "Vertical  Woolf."  The  error  is 
in  the  original.— C.  A.  S. 

tAs  these  computations  are  checks,  all  the  French  units  will  be  retained,  and  any- 
thing added  from  other  sources  will  be  put  in  ( ). 


THE  ALSA  TIAN  EXPERIMENT^  ETC.  231 


Heat  given  to  water  of  condensation,  Qt 29.1072  x  18.05  =  525.38  c. 

Q0_Qt  =  613.28  c.  —  525.38  c =    87.90    c. 

The  total  work  absorbed 72.79  c. 

The  external  radiation 7.      c. 

79.79  c. 

Instead  of  87.90;  or  an  error  of 87.90^-  79.79^  l  25         cent 

645.52 

The  heat  found  in  the  water  of  condensation  should  have  been  613. 28c. 
—79.79  c.  =  533.49  calories;  it  was  only  525.38  c.  consequently  too  little. 
The  total  heat  brought  to  the  machine  per  stroke  is  645.52  c.  which  to  be 
more  intelligible  we  will  transform  into  a  weight  of  dry  saturated  steam. 
In  accounting  for  the  work  of  the  engine  this  weight  will  serve  as  a  unit 
of  comparison  for  other  engines,  and  will  be  better  comprehended  under 
that  form  than  the  number  of  calories  expended  per  horse -power  which 
it  stands  in  place  of. 

Consumption  of  dry  steam  per  stroke,    645-52_°j_  =  0.98698  k. ;  weight 

654.03  c. 

of  dry  steam  per  total  horse-power  per  hour,  7,112  k.;  per  indicated 
horse  power,  8.614  k.;  per  net  horse-power,  9.864k.* 

II.- -I.  H.  P.,  267.85;  revolutions  per  min.,  25.2.;  net  on  brake,  226; 
mechanical  efficiency,  84.3  per  cent. 

Proportion  of  back  pressure  to  total  work  20.52  per  cent. 

"  back  pressure,  0.277  k.  (3.9  Ibs.). 
(Boiler  pressure,  60  Ibs.  above  atmosphere.) 

Per  Single  Stroke. 

Heat  brought  by  dry  saturated  steam 0.7124  k.  x  652.93  c.  =  465.14  c. 

"         "  entrained  water 0.0238  k.  x  153.74  c.  =      3.66  c. 

"  steam  to  jackets 0.0794  k.  x  499.19  c.  =     36.63  c. 

to  engine 505.43  c. 

"    kept  by  steam  leaving  condenser 0.7362  k.  x    29.10  c.  =  -21.42  c 

Qo 484.01  c. 

Heat  given  to, injection  water 29.3406  k.  x  14.3  c.  =  Ql  =  419.57  c. 


Difference  .....................................................     64.44  c. 

The  total  work  ...........................................  56.27  c. 

"    external  radiation  ..................................  7.     c. 

--    63.27  c. 


Error,  =0,i3  per  cent. 


The  heat  found  in  condenser  is  too  small,  it  should  have  been  484.01  — 
63.27  =  420.74  c. 

*These  weights  are  from  feed  water  at  Qo  c.    I  should  suggest  as  divisor  the  term 
Qo.—  C.  A.  S. 


232 


STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


The  heat  brought  per  stroke  is  505.43  c.;  it  represents  a  consumption 
of  dry  saturated  steam  of 


505.43 


=  0.77409  k. 


652.93 

Weight  dry  saturated  steam  per  hour  per  total  horse  power 6.945  k. 

"      "        "    indicated  horse  power  ..  8.739  k. 

"         "  "  •'        "      "       "    net  "          "       ..10.357k. 

III. — I.   H.   P.  185.75;    revolutions  per  minute,   25.4;    net  on  brake, 
145.52;  mechanical  efficiency,  78.3  per  cent. 

Proportion  of  back  pressure  work  to  total  work,  24.1  per  cent.;  back 
pressure  on  large  piston,  0.234  k.  (3.3  Ibs.). 

(Boiler  pressure  50  Ibs.  above  atmosphere.) 
Per  Single  Stroke. 

Heat  brought  by  dry  steam 0.5401  k.  x  650.69  c.  =  351.43  c. 

"  "        "    entrained  water 0.0145  k.  x  146.22  c.  =      2.12  c. 

"  "       steam  condensed  in  jacket  .  0.0640  k.  x  504.47  c.  =    32.28  c. 

Total 385.83  c. 

Heat  kept  by  steam  leaving  condenser 0.5546  k.  x    23.46  c.  =  —12.65  c. 

Qo 373.18  c. 

"    found  in  injection  water ?.  30.5688  k.  x  10.56  c.  =  Qa  =  322.80  c. 

Qo  —  Q! , 50.38  c. 

The  total  work 38.71  c. 

External  radiation . .  .    7.      c. 

45.71  c. 


Error. 


50.38  —  45.71 


=  1.2  per  cent. 


385.83 

The  heat  found  in  the  condenser  is  too  little,  it  should  have  been 
373.18—45.71  =  327.47  c. 

The  heat  brought  per  stroke,  b85.83c.;  it  represents  a  consumption 

of    385'83  =  0.59295  k. 
650.69 

Weight  of  dry  saturated  steam  per  hour  per  total  H.  P 7.384  k. 

"     "  "  "          "      "        "     ind.  H.  P 9.730k. 

"     "  "  "         "      "        "     net    H.  P 12.411k. 

Uniting  in  one  table  the  results  of  these  three  experiments,  we  find 
little  difference  per  total  horse-power,  only  3.7  per  cent,  for  a  change 
from  183  to  347  horse-power. 

TABLE  I. 


Force  indicated 

347 

267 

Steam  per  hour  per  total  H.  P..  kilos 

7.112 

6.945 

Back  pressure  work  in  per  cent,  of  total  work  

17.43 

20.52 

Steam  per  hour  per  indicated  H.  P 

8  614 

8  739 

Net  work  in  per  cent,  indicated  work       

87  30 

84  30 

Steam  per  hour  per  net  H.  P 

9  864 

10  357 

I. 


II. 


III. 


185 
7.384 
24.10 
9.730 
78.30 
12.411 


THE  ALSA  TIAN  EXPERIMENTS.  ETf '.  233 

We  note  that  the  cost  of  a  total  H.  P.  is  6  per  cent,  less  for  267  than 
for  185  horse-power.  This  economy  disappears  for  the  indicated  H.  P., 
which  is  best  for  347  H.  P. 

If  these  two  sorts  of  consumption  follow  a  distinct  law  we  owe  it  to 
the  back  pressure  work,  which  changes  to  17  per  cent,  from  24  per  cent. 
An  analagous  cause  produces  greater  differences  in  the  cost  of  a  net  H.  P. 
The  efficiency  changes  between  87  and  78  per  cent,  because  of  the  friction, 
and  we  are  not  astonished  to  see  the  cost  of  a  net  H.  P.  differ  by  20.5  per  cent. 
It  is  the  practical  loss  to  which  we  put  an  engine  working  at  185  H.  P.  which 
can  give  347,  and  is  due  to  the  back  pressure  and  friction.  But  we  should 
not  conclude,  as  is  often  done,  that  this  loss  is  due  to  throttling. 

The  difference  of  3.7  per  cent,  that  we  find  in  the  cost  of  a  total  H.  P. 
is  that  due  this  evil  influence,  and  is  very  little;  or  adding  the  slight  in- 
crease over  Experiment  II. 

I  then  legitimately  concluded  in  my  last  work  "  that  we  are  led  to 
adopt  the  most  simple  regulator,  an  expansion  variable  by  hand  and  a 
governor  throttle."  When  the  variations  of  work  are  large  we  can,  by 
hand,  without  stopping  the  engine,  change  the  introduction  for  the 
small  intermediate  differences  the  governor  acts  upon  the  valve.  It  is 
well  understood  that  we  do  not  here  speak  of  engines  where  the  force 
varies  nearly  instantly,  for  example,  to  double.  This  disposition  per- 
mits us,  as  we  have  seen,  to  obtain  all  the  benefits  of  a  prolonged  expan- 
sion, admitting  that  it  gives  a  notable  economy,  of  which  the  results  of 
the  following  experiments  will  permit  us  to  judge. 

"WOOLF"  BEAM  ENGINE  BY  ANDRE  KOECHLIN.  AT  MAiMERSPACH. 

Expansion  in  the  small  cylinder.  Checks  on  the  gauged  consumption 
from  the  heat  gained  by  the  injection  water. 

E. — I.  H.  P.,  143.11;  revolutions  per  minute,  26.2;  net  horse-power, 
118.38;  efficiency,  82.7  per  cent.;  back  pressure  work  in  per  cent,  of  total 
work,  18.6;  back  pressure  on  large  piston.  0.181  k.  (2.5  Ibs.);  expansion,  28 
times.    (Boiler  pressure,  67  Ibs.  above  atmosphere.) 
Heat  brought  by  dry  steam 0.3479  k.  x  654.03  c.  =  227.53  c. 

"  "      entrained  water 0.0200  k.  x  157.47  c.  =      3.15  c. 

"      steam  to  jackets. .  . .  0.0324  k.  x  496.56  c.  =    16.09  c. 


246.77  c. 
Heat  kept  by  steam  leaving  condenser 0.3679  k.  x    19.01  c.  =  — 6.93  c. 

"    expended,  Q0 239.78  c. 

"    rejected  in  condenser. .  21.8781  k.  x  9.06  c.  =  198.21  c. 


41.57  c. 

"    in  work    done 28.97  c. 

"    external  radiation 4.6    c. 

33.57  c. 

Error,       417=  3.2  per  cent. 


234  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 


The  heat  found  in  the  injection  water  is  too  small,  it  should  have  been 
239.78—33.57  =  206.21  c. 

The  total  heat  brought  to  the  engine  per  single  stroke  is  246.77  c.,  it 

94.fi  77 

represents  a  consumption  of  drv  steam  of - — =  0.3773  k. 

654.03 

Weight  of  dry  steam  per  hour  per  total  H.  P 6.731  k. 

"     <k        "        "        "     "    ind.   H.  P 8.273k. 

"  "  "  "  "  "  net  H.  P 10.019k. 

C.— I.  H.  P. ,215. 7;  revolutions  per  minute,  25.47;  net  on  brake,  185.69; 
mechanical  efficiency,  86.1  percent.;  back  pressure  work  in  per  cent,  of 
total  work,  15.6;  backpressure,  0.226  k.  (3.2  fts.);  expansion,  13;  (boiler 
pressure,  70  fibs,  above  atmosphere). 

Heat  brought  by  dry  steam 0.5338  k.  x  654.45  c.  =  349.34  c. 

"    entrained  water 0.0304  k.  x  158.88  c.  =      4.83  c. 

"    steam  to  jacket 0.0449  k.  x  405.57  c.  =    22.25  c 

Total 376.42  c. 

Heat  kept  by  steam  leaving  condenser 0.5642  k.  x  23.21  c.— 13.09  c. 

"      expended,  Q0 363.33  c. 

"      gained  by  injection  water 21.9136  k.  x  13.48  c.  =  295  39  c. 

67.94  c. 

"     in  work  done 44.83 

"     external  radiation 4.6 

Error,  67-24-49-43  =  4.9  per  cent.  49'«  c- 

376.42 

Heat  found  in  condenser  should  have  been 363.33—49.43  =  313.90  c. 

"    brought  per  single  stroke 376.42  c. 

376  42 
Represents  a  consumption  of  dry  steam — - —  =  0.5751  k. 

Dry  steam  per  hour  per  total  H.  P 6.878  k. 

"        "        "        "     "    ind.   H.  P 8.149k. 

"        "        "        "     "    net    H.  P 9.465k. 

F.— I.  H.  P.,  149.53;  revolutions  per  minute,  25.93;  net  on  brake,  124.74; 
mechanical  efficiency,  83.4  per  cent.;  back  pressure  work  in  per  cent, 
total  work,  17.5;  back  pressure  on  large  piston,  0.175  k.  (2.4  Ibs.);  expan- 
sion, 25. 

Heat  brought  by  dry  steam .0.3652  k.  x  654.03  c.  =  238.85  c. 

"    entrained  water 0.0210  k.  x  157.47  c.  =      3.30  c. 

"        to  jackets 0.0350  k.  x  496.56  c.  =    17.38  c. 

Total. : 259.53  c. 

Heat  kept  by  steam  leaving  condenser 0.3862  k.  x  19.43  c.  =  —7.50  c. 

"      expended,  Q0 252.03  c. 

"      given  to  injection  water 21.2674  k.  x  9.89  c.  =  Ql  =  210.33  c. 

41.70  c. 


THE  ALSA TIA N  EXPERIMENTS,  ETC.  235 


Heat  in  work  done  .......................................  30.51 

"      "  externa  Iradiation  ................................  4.6 

-       35.11  c. 

Error,  ==  2.5  per  cent. 


Heat  found  in  condenser  should  have  been  .......  252.03  -  35.11  =  216.92  c. 

Heat  expended  per  single  stroke  ..................................  259.53  c. 

Represents  dry  steam  ................................  259'53  =  0.3968  k. 

654.03 

Dry  steam  per  hour  per  total  H.  P  .................................  6.821  k. 

"      "      "    ind.  H.  P  .................................  8.260k. 

"      "      "    net    H.  P  .................................  9.898k. 

D.—  I.  H.  P.,  212.92;  revolutions  per  minute,  24.83;  net  on  brake, 
183.67;  mechanical  efficiency,  86.2  per  cent,;  back  pressure  work  in  per 
cent,  of  total  work,  14.9;  back  pressure  on  large  piston,  0.218  k.  (3  Ibs.); 
expansion,  13;  (boiler  pressure,  70  fos.  above  atmosphere). 

Heat  brought  by  dry  steam  ................  0.5443  k.  x  654.45  c.  =  356.22  c. 

"  entrained  water  ..........  0.0310  k.  x  158.88  c.  =      4.92  c. 

to  jackets  ..................  0.0462  k.  x  495.57  c.  =    22.89  c. 

Total  .....................  .............................  384.03  c. 

Heat  kept  by  steam  leaving  condenser  ____  0.5753  k.  x  27.02  c.  =    —  15.54  c. 

"    expended,   Q0  ............................................  ...  368.49  c. 

"    found  in  injection  water  ........  18.0071  k.  x  17.07  c.  =  Ql   =  307.38  c. 

61.11  c. 
"    in  work  done  ........................................  45.39 

"    "  external  radiation  ................................  4.6 

49.99  c. 


Heat  found  in  condenser  should  have  been.  ...368.49  —  49.99  =  318.50  c. 
Heat  brought  to  engine  per  stroke  .  ^  .........................  384.03  c. 

Represents  dry  steam  per  stroke  .............  .  38<L03  =  0.5867  k. 

654.45 

Dry  steam  per  hour  per  total  H.  P  .................................  6.983  k. 

"      "      ind.  H.  P  .................................  8.210k. 

"      "      net  H.  P  .................................  9.517k. 

This  Malmerspach  engine  is  composed  of  two  coupled  on  the  same 
shaft,  and  experiments  E  and  C  were  made  on  the  left,  while  experiments 
F  and  D  were  made  on  the  right-hand  engine.  We  note  that  three  of 
these  experiments,  E,  F,  D,  check  to  3  per  cent,  nearly,  but  C  only  to  5 
per  cent.;  however  the  direct  measurement  is  correct,  being  sensibly  that 
of  experiment  D. 


236 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


TABLE  II. 


E. 

F. 

C. 

D. 

Expansion            

28 

' 
25 

13 

13 

I  H  P  ,  Cfa.  de  V        

143 

149 

215 

213 

Dry  steam  per  hour  per  total  H   P  .  ks. 

6  731 

6.821 

6.878 

6.983 

Per  cent   back  pressure  work        ...  .... 

18.6 

17.5 

15.6 

14.9 

Dry  steam  per  hour  per  ind.  H.  P.,  ks.  .  . 
Per  cent,  of  mechanical  efficiency  
Dry  steam  per  hour  per  net  H.  P.,  ks  

8.273 
82.7 
10.019 

8.260 
83.4 
9.898 

8.149 
86.1 
9.465 

8.210 
86.2 
9.517 

Table  II.  sums  our  four  experiments.  The  figures  which  are  there, 
compared  with  Table  I.,  permit  us  to  decide  if  it  is  more  advantageous  to 
work  with  the  throttle  than  with  a  cut-off  in  the  small  cylinder,  or  the  re- 
verse. If  one  is  obliged  to  produce  from  an  engine  too  small  a  power,  either 
way  is  used,  but  for  a  careful  comparison  it  is  necessary  to  take  if  possible 
the  work  with  the  same  difference  in  each.  For  example,  Malmerspach 
Engine  C  and  E;  I.  H.  P.,  215  and  143,  being  3.2;  expansions,  13  and  28; 
and  the  Miinster  engine,  II.  and  III.,  I.  H.  P.,  267  and  185,  being  nearly 
the  same  ratio,  expansion  7. 

In  dry  steam  per  hour  per  total  H.  P.  there  is  a  difference  between 

6.945  k.,  with  267  H.  P.,  and  7.384  k.,  with  185  H.  P.  of  Zi^J^?l5  =  5.9 

7.oo4 

per  cent,  in  favor  of  the  larger  power,  both  obtained  by  throttling. 

If  in  the  second  engine  we  pass  from  expansion  13  to  28,  the  differ- 


ence in  dry  steam  per  total  H.  P.  is 


G.878  —  6.731 
6.878 


=  2.1  per  cent,  in  favor  of 


the  lesser  power,  143  H.  P.,;  in  these  limits  there  is  little  to  choose,  for  the 
difference  is  within  the  errors  of  observation. 

It  seems  as  if  there  was  an  economy  of  5.9  +  2.1  =  8  per  cent.;  on  the 
other  hand,  the  267  H.  P.  corresponds  to  the  least  consumption,  6.945  k. 
which  has  been  obtained  by  throttling  1.342  k.  at  the  cut-off  (18.8  ft>s.).  As 

this  only  differs  6>94AzL6j^I?  =0.9  per  cent,  from  that   for  215  H.  P., 


we  conclude,  as  before,  that  it  is  unimportant. 

We  find  ourselves  here  in  the  face  of  a  contradiction  which  we  can 
elucidate  later  after  having  given  the  complete  analysis  of  these  engines. 
For  the  time  we  have  only  to  note  how  the  heat  of  the  injection  water  checks 
the  consumption  and  fixes  the  degree  of  confidence  which  we  should  give 
to  each  experiment. 

These  remarks,  based  upon  the  amounts  used  per  total  H.  P.  per  hour, 
only  refer  to  the  work  of  the  steam  itself  in  the  cylinder.  They  are  not 
affected  by  poor  vacuum,  nor  the  friction  of  the  engine.  The  influence 
of  these  two  elements  is  only  felt  when  we  consider  the  indicated  work 
and  the  net  work.  Thus,  in  passing  from  experiment  E  143.  H.  P.,  ex- 
pansion, 28,  to  experiment  C,  215  H.  P.,  expansion  13,  the  consumptions 
differ  per  indicated  H.  P.  1.5  per  cent,  and  per  net  H.  P.  5.5  per  cent. 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  237 

This  difference  is  in  the  reverse  order  of  that  for  the  total  H.  P.;  it  shows 
that  practically  there  is  5.5  per  cent,  loss  in  changing  from  expansion  13 
to  28.  These  same  causes,  back  pressure  work  and  friction,  have  brought 
for  the  Munster  engine,  with  fixed  expansion  7,  stronger  effects — increased 
to  16J  per  cent,  when  throttle  causes  the  work  to  fall  from  267  H.  P.  to  185 
H.  P. 

Upon  the  same  engine  at  Malmerspach,  and  before  the  application  of 
expansion  gear,  there  had  been  made  an  experiment,  with  the  object  of 
defining  the  economy  realized,  which  we  will  check  as  before. 

B.— Indicated  H.  P.,  201.64  H.  P.;  revolutions  per  minute,  24.18;  net 
on  brake,  172.80  H.  P.;  mechanical  efficiency,  85.6  per  cent.:  back  pressure 
work  in  per  cent,  of  total  work,  16.4;  back  pressure,  0.235  k.  (3.3  Ibs.  per 
sq.  in.);  expansion,  6;  (boiler  pressure,  67  tt>s.  above  atmosphere). 

Heat  brought  by  dry  steam 0.5823  k.  x  654.03  c.  =  380.84  c. 

"    entrained  water 0.0312  k.  X  157.47  c.  =      4.91  c. 

to  jackets 0.0330  k.  x  496.56  c.  =    16.38  c. 

Total ' 402.13  c. 

Heat  kept  by  steam  leaving  condenser 0.6135  k.  x    22.73  c.  =    13.94  c. 

"      expended,  Q0 388.19  c. 

found  in  injection  water 22.6234  x  14.50  =  Ql  =  328.04  c. 

60.15  c. 

"      in  work  done 44.14  c. 

"      "    external  radiation 4.6    c. 

48.74  c. 

Error  ^^8-^  =  2.8  per  cent. 

The  heat  found  in  injection  is  too  small;  it  should  have  been  388.19  — 
48.74  =  339.45  c.  The  heat  per  stroke  is  402.13  c. 

It  represents  4?i4i  =  0.6148  k.  dry  steam. 
654.  Oo 

Dry  steam  per  hour  per  total  H.  P 7.402  k. 

a    ind.  H.P 8.847k. 

"    net    H.P 10.301k. 

The  result  of  this  analysis,  if  we  consider  the  engine  in  good  order 
when  the  experiment  was  made,  which  we  will  suppose  to  be  the  case, 
compared  with  experiment  C. 

B. — Expansion  6,  C.— Expansion  13. 
Per  Total  H.  P.  -7'402  ~  6'878    =  7.1  per  cent. 

Per  Ind.    H.  P.  8'847  ~  8'149    =  8  per  cent. 


Per  Net.  H.  P.  10'3  ^66  =  8  per  cent. 


by  C  over  B. 


238  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

I  have  valued  the  friction  by  the  brake  experiments  of  our  Mechanical 
Committee.  We  shall  see  how  far  MM.  Powell  have  obtained  the  same  co- 
efficients upon  their  "Woolf "  engines. 

HORIZONTAL    "WOOLF"  ENGINE,    BY    ANDRE  KOECHLIN,   TEIED   WITH  BRAKE 
BY  THE  MECHANICAL   COMMITTEE. 

I.— I.  H.  P.,  130;  revolutions  per  minute,  39.37;  net  on  brake,  112.08; 
mechanical  efficiency,  86.1  per  cent.;  back  pressure  work  in  per  cent,  of 
total  work,  20.06;  back  pressure,  0.253  k.  (3.5  Ibs.);  expansion,  6;  (boiler 
pressure,  53  Ibs.  above  atmosphere). 

Heat  brought  by  dry  steam 0.2286  k.  x  652.46  c.  =  149.15  c. 

"    entrained  water 0.0079  k.  x  152.17  c.  =      1.20  c. 

to  jackets .0.0263  k.  x  500.29  c.  =    13.16  c. 

Total 163.51  c. 

Heat  kept  by  steam  leaving  condenser . .  .0.2365  k.  x  26.20  c.  =     6.19  c. 

expended,  Q0 157.32  c. 

"      found  in  injection  water 14.6202  k.  x  9.20  c.  =  134.50  c. 

22.82  c. 

"     in  work  done 17.45  c. 

14     in  external  radiation 3.5    c. 

20.95  c. 

Error  ?2^p  =  1.13  per  cent. 

The  heat  gained  by  injection  should  have  been  157.32  —  20.95  =  136.37  c. 
Heat  per  single  stroke 163.51  c. 

Represents  dry  steam  per  stroke. .  .  .^-r1  =  0.2506  k. 

652.46 

Dry  steam  per  hour  per  total  H.  P 7.290  k. 

"      ind.  H.  P 9.120k. 

"  net  H.  P 10.563k. 

There  is  only  1.3  per  cent,  difference  between  the  consumption  per 
total  H.  P.,  and  that  in  experiment  B;  while  for  the  indicated  H.  P.  there 
is  3  per  cent,  in  the  other  direction. 

II.— I.  H.  P.,  181;  revolutions  per  minute,  39.67;  net  on  brake,  161  H. 
P.;  mechanical  efficiency,  89  per  cent.;  back  pressure  work  in  per  cent,  of 
total  work,  17.3;  back  pressure,  0.295  k.  (4.1  Ibs.);  boiler  pressure,  54  Ibs. 
above  atmosphere). 
Heat  brought  by  dry  steam 0.3134  k.  x  652.69  c.  =  204.55  c. 

"    entrained  water 0.0134  k.  x  152.96  c.  =      2.05  c. 

to  jackets 0.0271k.  x  499.73  c.  =    13.54  c. 

Total 220.14  c. 

Heat  kept  by  steam  leaving  condenser 0.3268  k.  x  23.90  c.  =      7.81  c. 

"     expended,  #0 212.33  c. 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  239 

Heat  rejected  in  injection  water 14.5795  k.  x  12.58  c.  =  183.41  c. 

212.33  —  183.41    =    28.92  c. 

"  in  work  done 24.12 

"  in  external  radiation .  3.50 

27.62  c. 

Error  ^-^  =  0.6  per  cent. 

Heat  brought  per  stroke 220.14  c. 

Represents  dry  steam  per  stroke 22(U4  =  0.3372  k. 

Dry  steam  per  hour  per  total  H.  P 7.328  k. 

"  ind.  H.  P 8.878k. 

"  net  H.  P 9.975  k. 

The  consumption  per  total  H.  P.  is  nearly  the  same  as  for  the  preced- 
ing experiment,  but  for  the  indicated  and  net  H.  P.  there  is  a  marked 
improvement  by  better  efficiency,  and  less  proportion  of  back  pressure 
work,  although  the  vacuum  is  not  so  good.  This  is  a  fact  which  we  have 
many  times  noted. 

Finally,  that  we  may  not  lack  generality  in  our  conclusions  of  the 
influence  of  expansion  in  the  small  cylinder,  I  will  give  the  results  of  ex- 
periments made  upon  the  engines  constructed  by  MM.  Powell.  Little 
different  from  the  preceding,  they  are  designed  with  a  view  to  an  early 
cut-off  in  the  small  cylinder,  but  distinguish  themselves  by  the  excellent 
vacuum,  0.100  k.  of  back  pressure  (1.4  Ibs.)  on  the  large  piston.  We  shall 
see  that  for  19  expansions  the  consumption  per  total  H.  P.  is  nearly  the 
same  as  that  we  have  found  for  13  and  28  times. 

"WOOLF"  BEAM  ENGINE  BY  POWEIZL,   WORKING  AT   ST.   BEMY. — EXPERIMENT 

BY  M.  R.  QUEM. 

Expansion,  19  times;  indicated  horse-power,  137;  revolutions  per  min- 
ute, 24.503;  net  on  brake,  107.88  H.  P. ;  mechanical  efficiency,  78.7  per  cent.; 
back  pressure  work  in  per  cent,  of  total  work,  9.9;  back  pressure,  0.102  k. 
(1.4  tbs.);  (boiler  pressure,  70  Ibs.  above  atmosphere). 

Heat  brought  by  dry  steam 0.3222  k.  x  654.42  c.  =  210.85  c. 

"    entrained  water 0.0110  k.  x  158.80  c.  =      1.75  c. 

to  jackets 0.0412  k.  x  495.62  c.  =    20.42  c. 

Total 233.02  c. 

Heat  kept  by  steam  leaving  condenser 0.3332  k.  x  27  c.  =  — 8.99  c. 

expended,  Q0 224.03c. 

found  gained  by  injection  water. .     .  .10.8511  k.  x  18.24  c.  =  197.92  c. 


26.11  c. 

in  work  done 29.79 

in  radiation 4.50 

34.29  c. 


24O  STEAM  USING;  OE,  STEAM  ENGINE  PRACTICE. 

Heat  found  should  have  been 224.03  —  34.29  =  189.74  c. 

"    per  single  stroke 233.02  k. 

Kepresents  dry  steam. .  .  233'02  =  0.356  k. 

654.42 

Heat  per  hour  per  total  H.  P 6.840  k. 

"      •'       "      "     ind.  H.   P 7.591k. 

"  "  "  "  net  H.  P 9.702k. 

The  consumption  per  total  H.  P.  of  this  last  experiment,  made  with 
19  expansions  on  the  Powell  engine,  is  exactly  between  the  two  experi- 
ments E  and  C,  made  upon  the  Koechlin  engine  with  expansions  of  13 
and  28.  These  three  consumptions  are  6.731  k.,  6.840  k.,  6.878  k.,  differing 
among  themselves  1.4  per  cent.  Upon  different  engines  they  prove,  be- 
tween expansions  of  13  and  28,  how  little  the  effect  of  expansion  is  upon 
the  good  work  of  steam.  The  very  good  vacuum  of  the  Powell  engine, 
0.102  k.  (1.4  Ibs.),  gives  it  practically  a  marked  superiority  over  the 
Koechlin  engine,  expanding  13  times,  a  circumstance  remarkably  excep- 
tional for  a  "Woolf  "  engine,  which  demands  justification  by  more  numerous 
experiments  ;  it  loses  only  9.9  per  cent,  in  back  pressure  work,  in  the 
place  of  15  per  cent.,  and  we  shall  not  be  astonished  to  find  there  is 

S'M9  ~^A  ?'591  =  6'8  Per  cent-  in  its  favor' 
o.i^y 

We  had  wished  to  join  in  these  results  those  that  were  obtained  by  M. 
H.  Koland  upon  the  same  Powell  engines,  tried  at  Bolbec ;  but,  as  we 
shall  see,  their  exactitude  leaves  much  to  be  desired,  and  we  only  remark 
the  excellent  vacuum  and  the  error  committed,  9.9  per  cent.,  which  causes 
us  to  set  aside  the  results.* 

The  results  of  the  experiments  C,  D,  E,  F,  of  the  Malmerspach  engine, 
built  by  Andre  Koechlin,  with  that  on  the  St.  Remy  engine,  by 
Powell,  prove  to  us  the  small  influence  of  an  expansion  from  13  to  28 ;  in 
these  limits  the  total  H.  P.  cost  varies  only  2  per  cent,  in  one  case  from 
the  other.  This  fact  acquired,  we  shall  seek  to  render  an  account  of  the 
following  anomaly,  which  we  have  already  noted,  between  cost  per  total 
H.  P.  of  experiments  B  and  C  of  the  Malmerspach  engine.  With  expan- 
sion 6  and  13  we  found  7  per  cent,  difference,  which  should  represent  the 
economy  of  expansion  13  ;  but  we  should  be  too  high,  for  it  does  not 
agree  with  the  figures  of  C,  D,  E  and  F,  nor  with  the  results  of  the 
Powell  engine.  This  difference  is  more  when  compared  with  II.,  267  H. 
P.,  of  the  Munster  engine,  expanding  7  times,  which  gives  the  least  cost 
as  6.945  k.  per  total  H.  P.,  when  the  expansion  13  gives  6.878  k. — difference 
of  1  per  cent.  We  shall  see  if  analysis  will  show  us  the  cause  of  this  irre- 
gularity. 

ANALYSIS   OF  EXPERIMENT  III. 

Account  of  heat  and  cooling  by  condenser,  per  stroke: 

Weight  of  fluid  in  small  cylinder 0.5776  k. 

"  dry  steam  at  cut-off 0.4553  k. 

"The  computations  are  not  transcribed. — C.  A.  S. 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


TJU,  31 T  7 


Weight  of  water  at  cut-off  (21.17  per  cent.) 0.1223  k. 

"        "      "     entrained 0.0145  k. 

"  "  "  condensed  up  to  cut-off 0.1078  k. 

Heat  given  to  iron 0.1078  k.  x  516.77  c.  =  55.70  c. 

Weight  of  fluid  in  large  cylinder 0.5830  k. 

"         "  dry  steam  at  end  of  stroke 0.5399  k. 

"        "  water  at  end  of  stroke  (7.39  per  cent.) 0.0431  k. 

Internal  heat  at  the  end  of  admission,  U0 — 290.12  c. 

Internal  heat  at  the  end  of  stroke,  U1 322.01  c. 

U0—  Uj 31.89  c. 

Heat  given  by  jacket 32.28  c. 

"        "       "  condensation  in  small  cylinder 55.70  c. 

"    furnished  during  expansion  56.09  c. 

"    absorbed  by  total  work  of  expansion 35.61  c. 

"    radiated  externally 7.00  c. 

42.61  c. 

56.09  —  42.61  =  13.48  c.  =  Re,  cooling  by  condenser  being  3. 5  per  cent, 
of  the  heat  brought  to  the  engine. 

The  final  internal  heat  compared  with  the  heat  gained  by  the  injection 
water  furnishes  a  check  on  Re. 

Internal  heat  at  end  of  stroke,  Ul 322.01  c. 

Heat  of  back  pressure  work +  12.29  c. 

"    remaining  in  cushion —  14.92  c. 

after  condensation —  12.65  c. 

306.73  c. 
"    gained  by  injection  water 322.80  c. 

Re 16.07  c. 

The  other  method  gave  Re  —  13.48  c.;  the  error  is  only 

*1^?  •?«*-* 

ANALYSIS    OF    EXPERIMENT    II. 

Account  of  heat  and  cooling  by  the  condenser: 

Weight  of  fluid  in  small  cylinder 0.7697  k. 

"        '•'  dry  steam  at  cut-off 0.6603  k. 

"        "  water  at  cut-off  (14.21  per  cent.) 0.1094  k. 

"        "      "      entrained 0.0238k. 

"       "      "      condensed 0.0856  k. 

Heat  given  to  iron  up  to  cut-off. .  .  43.40  c. 


242  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

Weight  of  fluid  in  large  cylinder 0.7650  k. 

"        "  drv  steam  at  end  of  stroke. .  . .  0.7237  k. 


"  water  at  end  of  stroke  (5.39  per  cent.) 0.0413  k. 

Internal  heat  at  cut-off,  TJ0 415.57  c. 

Internal  heat  at  end  of  stroke,  Ul 432.15  c. 

U0  —  Uj —  16.58  c. 

Heat  furnished  by  jacket 36.63  c. 

"         "    condensation  in  small  cylinder 43.40  c. 

"        during  expansion 63.45  c. 

"    absorbed  by  work  of  expansion 49.80  c. 

"    external  radiation 7.      c. 

56.78  c. 

Re  =  6.65  c.;  jRc  is  a  loss  of    6         =  1.32  per  cent,  of  total  heat  per 

505.43 

stroke  furnished  engine. 
Check  on  Re: 

Internal  heat  at  end  of  stroke,  U^ 432.15  c. 

Back  pressure  work +  14.53  c. 

Heat  remaining  in  cushion —  15.13  c. 

Heat  remaining  in  fluid  after  condensation —  21.42  c. 

410.13  c. 
Heat  gained  by  injection  water 419.57  c. 

Re 9.34  c. 

The  other  method  Re  =  6.65;  9j4t  ~  6'65  =  .55  per  cent. 

505.45 


ANALYSIS    OF   EXPEBIMENT   I. 

Account  of  heat  and  cooling  by  condenser,  Re: 

Weight  of  fluid  in  small  cylinder  per  stroke 0.9847  k. 

dry  steam  at  cut-off 0.8254  k. 

water  at  cut-off  (16.17  per  cent.) 0.1593  k. 

water  entrained  . .  .  .0.0290  k. 


water  condensed  at  cut-off 0.1303  k. 

Heat  given  to  iron  at  cut-off 65.25  c. 

Weight  of  fluid  in  large  cylinder 0.9691  k. 

dry  steam  at  end  of  stroke 0.9051  k. 

water  at  end  of  stroke  (6.6  per  cent.) 0.0640  k. 

Internal  heat  at  cut-off,  U0 525.79  c. 

"     end  of  stroke,  U, 543.19  c. 

U—U...  17.40  c. 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  243 

Heat  furnished  by  jacket 43.89  c. 

by  iron  small  cylinder 65.25  c. 

during  expansion 91.74  c. 

Heat  in  total  work  done  during  expansion 62.85  c. 

Heat  of  external  radiation 7.00  c. 

.Re  =  21.89  c.;  per  cent,  of  heat  furnished,  3.38. 

Check  on  Re.: 

Internal  heat  at  end  of  stroke,  Ul 543.19  c. 

Back  pressure  work +  15.37  c. 

Heat  remaining  in  cushion —  14.60  c. 

fluid  after  condensing 32.24  c. 

511.72  c. 

Heat  gained  by  injection  water 525.38  c. 

Re 13.66  c. 

The  other  method  gave  21.89: 

Error,  ^'^^M  =  1-26  per  cent. 

HOBIZONAL  "WOOLF,"  130  H.  P.;  EXPANSION,  6. 

Account  of  heat  and  cooling  by  condenser  Re: 

Weight  of  fluid  per  stroke  in  small  cylinder 0.2500  k. 

dry  steam  at  cut-off 0.2220  k. 

water  at  cut-off  (11.2  per  cent.) 0.0280  k. 

water  entrained . .  . .  0 . 0079  k. 


water  condensed  at  cut-off 0.0201  k. 

Heat  given  to  iron  at  cut-off 10.30  c. 

Weight  of  fluid  in  large  cylinder 0.2506  k. 

dry  steam  at  end  of  stroke . .  .0.2372  k. 


water  at  end  of  stroke  (5.34  per  cent.) 0.0134  k. 

Internal  heat  at  cut-off,  U0 . .137.85  c. 

*     end  of  stroke,  Ut 141 .48  c. 

Z7o  —  #i .—3.63  c. 

Heat  furnished  by  jacket 13 . 16  c. 

"  iron  above..  .  10.30  c. 


during  expansion 19 . 83  c. 

Heat  absorbed  during  expansion,  total  work 14.38  c. 

"     external  radiation 3 . 50  c. 

Re  =  1.95  c.;  per  cent.  Re  of  total  heat  furnished,  1.19  c. 
Check  on  Re. : 

Internal  heat  at  end  of  stroke 141 .48  c. 

Back  pressure  work . .  +4 . 38  c. 


244  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE, 


Heat  retained  in  cushion  .........................................  —  7.43  c. 

in  condenser  .......................................  —  6  .  19  c. 

132.  24  c. 
gained  by  injection  water  ...............  ..............  .......  134.53  c. 

Re  ............................................................     2  .  26  c. 

Error,  2.-2_lj.?5  =  0>1  percent. 


HOKIZONTAL   "WOOLF,"   181    H.  P.;   EXPANSION,    6. 

Account  of  heat  and  cooling  by  condenser  Re: 
Weight  of  fluid  per  stroke  in  small  cylinder  .....................  0.3459  k. 

"        dry  steam  per  stroke  at  cut-off  .........................  0.3082  k. 

"        water  per  stroke  at  cut-off  (10.8  per  cent.)  .....  ........  0.0377  k. 

"        water  entrained  ............................  .  ...........  0.0134  k. 

"        water  condensed  at  cut-off  ........  .  ....................  0.0243  k. 

Heat  given  to  iron  ...............................................     12.24  c. 

Weight  of  fluid  in  large  cylinder  .................................  0.3478  k. 

"        dry  steam  at  end  of  stroke  .............................  0.3324  k. 

"        water  at  end  of  stroke  (4.5  per  cent.)  ..................  0.0154  k. 

Internal  heat  at  end  of  admission,  U0  ............................  192.68  c. 

"   stroke,  U,  ........................  ........  198.80  c. 

U0  —  Ui  ...........................  .  ..........................  —6.12  c. 

Heat  furnished  by  jacket  .........................................  13.54  c. 

"    iron  above..  .  12.24  c. 


during  expansion 19.66  c. 

"    absorbed  during  expansion,  total  work 14.50  c. 

"    lost,  external  radiation 3.50  c. 

Re  -  1.66  c.;  per  cent,  of  heat  furnished  -— 6~  =  0.75. 

220.14 

Check  on  Re. : 

Internal  heat  at  end  of  stroke,  U^ 198.80  c. 

Back  pressure  work +5.10  c. 

Heat  retained  in  cushion — 10.03  c. 

"  "  condenser. .  .  —7.81  c. 


186.06  c. 
gained  by  injection  water 183.41  c. 


Re 2.65  c. 

The  other  method  ga"Ve  1.66  c. 

6  *  °-45  per  cent- 


THE  A  L SA  TIA  JV  EXPERIMENTS,  ETC.  245 


The  error  appears  to  be  2'6^  1>66  =  1.9.  As  the  check  on  Re  gives 
—  2.65,  the  injection  has  gained  less  heat  than  was  rejected.] 

Experiment  II.  on  the  Munster  engine  and  I.  on  the  horizontal  engine 
differ  little  as  to  proportions  of  final  water  and  heat  lost  by  the  cooling 

due  the  condenser  Re.    We  have  stated  the  difference  7A2^~l|^7i5  =  4.7 

7.290 

per  cent,  between  the  cost  of  a  total  H.  P.  It  is  due,  part  to  the  differ- 
ence between  6  and  7  expansions,  but  more  to  the  strong  compression  in 
the  vertical  engine  which  partially  annuls  the  effect  of  the  clearance. 

The  experiments,  of  which  the  analyses  will  follow,  do  not  offer  the 
precision  of  the  two  preceding  series,  of  which  the  consumption  checks 
within  one  per  cent.,  nearly;  also  we  will  neglect  the  weight  of  fluid  in  the 
clearance  when  establishing  the  internal  heats  Ul  and  U0  and  the  differ- 
ence U9  —  ZTi.  I  did  not  proceed  thus  until  I  had  rendered  an  account  of 
the  error  which  is  committed. 

With  engine  267  H.  P.,  U0  —  £7,  =  16.58  c.;  when  the  clearance  is  taken 
into  account,  U0  —  Ul  =  19.80  c.;  when  it  is  neglected,  there  is  an  error  of 

XM°  -  1M§  =  0.6  per  cent.    For  the  horizontal  engine,  U0  —  U,  will  be 
505.4)3 

3.44  in  place  of  3.63  c.,  an  error  of  M3  +  3._44  =  0.1  per  cent. 

loo. 51 

Our  second  manner  of  procedure  is  thus  justified  above  all  in  the 
practical  experiments  which  check  within  3  per  cent,  only,  but  we  add 
again  that  this  approximation  is  very  satisfying  and  conducts  us  to  some 
very  remarkable  results.  [The  error  is  always  one  way,  and  the  compari- 
sons are  very  accurate] . 


MALMERSPACH  ENGINE,    EXPERIMENT  A— 201    H.   P.,   EXPANSION,   6. 

Heat  account  and  cooling  by  condenser  Re: 

Weight  of  fluid  in  small  cylinder 0.6135  k. 

"      "  dry  steam  at  cut-off 0.5350  k. 

"      "  water          •<        "     (12.8  per  cent.) 0.0785  k. 

"      "      "      entrained 0.0312k. 

"  "  "  condensed  at  cut-off 0.0473k. 

Heat  given  to  iron 24.09  c. 

Weight  of  fluid  in  large  cylinder 0  6135  k. 

(<      "  dry  steam  at  end  of  stroke 0.5429  k. 

"      "water          "         "         "       (11.5  per  cent.) 0.0706k. 

Internal  heat  at  end  of  admission,  U0 384.86  c. 

"   stroke,  ^ 327.69  c. 

U0—  U,..  7.17  c. 


246  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

Heat  furnished  by  jackets 16.38  c. 

«  "  «    iron.  .  24.09  c. 


during  expansion ...     47.64  c. 

"    absorbed        "  "  by  total  work 34.60  c. 

"    lost  by  external  radiation 4.60  c. 

Q       A    A 

Rc  =  8.44  c..  being  -  =  2.1  per  cent,  of  the  heat  furnished. 

402.13 

Check  on  .Rc: 

Internal  heat  at  end  of  stroke,  t/i 327.69  c. 

Back  pressure  work 8.61  c. 

Heat  retained  after  condensation.  .  . . — 13.94  c. 


322.26  c. 
Heat  gained  by  injection  water 328.04  c. 

.Rc 5.68  c. 

By  the  other  method 8.44  c. 

Error,  8^^8  =  0.7  per  cent. 

This  engine  differs  from  the  horizontal  one  by  a  larger  proportion  of 
terminal  water,  11.5  per  cent,  in  place  of  5.3  per  cent.  The  cost  of  a  total 

H.  P.  is  also  greater  by  I^^—J'290  =  1.5  per  cent. 

The  expansion  6  and  the  conditions  of  regulation  are  the  same,  but 
we  see  that  the  jackets  are  not  working  in  the  same  manner  as  those  of  the 
horizontal  engine  condensing  10  per  cent,  of  the  steam,  while  the  second 
is  only  5.1  per  cent.;  there  is  then  from  this  fact  a  loss  which  changes  the 
internal  heat  and  increases  the  heat  lost  by  the  cooling  due  the  con- 
denser. 

Compared  with  Experiment  II.,  267  H.  P.,  Experiment  B  gives  us  4.7 
per  cent,  less  condensation  in  the  jackets  and  a  less  cushion,  which  brings 

the  Malmerspach  engine  — — "~ '    ' —   =  6.1  per  cent,  worse  than  the 

Munster  engine.  All  these  considerations  should  indicate  where  the 
economy  really  is  rather  than  to  a  large  expansion  commencing  in  the 
small  cylinder. 

MALMEKSPACH  ENGINE — EXPERIMENT  C.,  215  H.  P.;    EXPANSION    13. 

Account  of  heat  etc.,  per  stroke: 

Weight  of  fluid  in  small  cylinder 0.5642  k. 

"      "  dry  steam  at  cut-off 0.4303  k. 

"      "  water  "        "    (23.7  per  cent.) 0.1339  k. 

"      "       "     entrained..  0.0304k. 


condensed  at  cut-off. .  0.1035  k. 


THE  ALSATIAN  EXPERIMENTS,  ETC.  247 

Heat  given  to  iron 51.30  c. 

Weight  of  fluid  in  large  cylinder 0.5642  k. 

"      "  dry  steam  at  end  of  stroke 0.4632  k. 

"      "  water           "           "             (17.9  per  cent.) 0.1010  k. 

Internal  heat  at  end  of  admission,  U0 283.55  c. 

"    "    "     "    stroke,  U1: 282.31  c. 

U0— H! 1.24  C. 

Heat  furnished  by  jackets 22.25  c. 

"     iron..  51.34  c. 


Total  heat  furnished  during  expansion 47.83  c. 

Heat  in  total  work  done 38.79  c. 

"      "    external  radiation 4.60  c. 

Re  -  32.44c,  being   31'44=  8.3  percent,  of  the  entire  heat  furnished. 
376.42 

The  check  on  Re  is  not  as  exact  as  before;  but  as  we  remember  that  in 
this  experiment  the  error  was  5  per  cent.,  while  in  the  others  it  was  about 
2.5  per  cent.,  this  is  not  surprising. 

Internal  heat  at  end  of  stroke,  U0 283.31  c. 

Back  pressure  work 8.48  c. 

Heat  retained  in  condensed  water . .  . .  —    13.09  c. 


277.70  c. 
"    gained  by  injection  water 295.39  c. 

Re 17.69  c. 

The  other  method  gave  31.44;  31'44~17-69=  3.7  per  cent,  error. 

376.42 

The  other  experiments  were  much  closer. 

The  cut-off  in  the  small  cylinder  being  much  earlier,  it  is  desirable 
to  calculate  the  internal  heat  Z72  at  the  end  of  the  stroke  in  the  small 
cylinder. 

Weight  of  fluid  in  small  cylinder 0.5642  k. 

"  dry  steam  at  end  of  its  stroke 0.4901  k. 

Internal  heat,  Z72 305.84  c. 

MALMERSPACH  ENGINE — EXPERIMENT.  D.,  213  H.    P.;  EXPANSION,  13. 

Account  of  heat,  etc.,  per  stroke: 

Weight  of  fluid  in  small  cylinder '. 0.5753  k. 

"          "   dry  steam  at  cut-off. .  0.4328k. 


"  water  (24.7  per  cent.) 0.1425  k. 

"      "    entrained..  0.0310k. 


;    condensed  at  cut-off ...     0.1115k. 

Heat  given  to  iron 55.31  c. 


248  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

Weight  of  fluid  in  large  cylinder 0.5753  k. 

"          "  dry  steam  at  end  of  stroke 0.4628  k. 


'  water                                     (19.5  per  cent  ) 0.1121  k. 

Internal  heat  at  cut-off,  U0 286.44  c. 

"  end  of  stroke,  Ut 283.20  c. 

U0—  Ul 3.24  c. 

Heat  furnished  by  jacket 22.89  c. 

"   iron..  55.31  c. 


during  expansion 81.44  c. 

"      taken  by  total  work  of  expansion 39.04  c. 

"            "      "  external  radiation 4.06  c. 

.Re 37.80  c. 

or?  on 

Per  cent,  of  entire  heat  -'      ~n=  9.9  per  ce nt. 

OO4:.'  10 

The  check  on  Re: 

Internal  heat  at  end  of  stroke,  ^ 283.20  c. 

Back  pressure  work 7.97  c. 

Heat  retained  after  condensation . .  .  15.54  c. 


275.63  c. 

"    gained  by  injection  water 307.38  c. 

Re 31.75  c. 

Error,    37'80  ~  81-7S=1.6  per  cent. 
384.03 

At  the  end  of  stroke  in  small  cylinder,  C/",: 

Weight  of  fluid 0.5753  k. 

"         dry  steam 0.4928  k. 

"  water  (1.43  per  cent.) 0.0825  k. 

Internal  heat  at  end  of  stroke  in  small  cylinder 308.79  c. 

These  two  experiments  with  the  same  expansion,  13,  are  made,  one 
on  the  right  engine,  the  other  on  the  left,  and  give  results  little  different. 

Thecost  per  total  H.  P.  of  C.  is  only  6 •  983g  ~  6 • 878  =  1.5  per    cent. 

6 . 982 
better  than  D. 

The  proportions  of  water  for  C  and  D  respectively  are  at  cut-off,  23.7 
and  24.7  per  cent.;  at  the  end  of  the  stroke  in  small  cylinder,  13.1  and 
14.3  per  cent.,  and  at  the  end  of  stroke  in  large  cylinder,  17.9  and  17.5  per 
cent.,  following  nearly  the  1J  per  cent,  difference. 

Re  differs  8.3  and  9.9  per  cent.,  only  1.6  per  cent. 

We  will  take  for  comparison  experiments  B,  expansion  6;  C,  expansion 
13,  and  E,  expansion  28,  all  made  on  the  left-hand  engine. 

The  last  two  experiments  throw  light  upon  a  fact  which  should,  above 
all,  attract  our  attention.  It  is  the  great  evaporation  which  takes  place  in 
the  small  cylinder  during  the  first  expansion.  The  introduction  at  full 
pressure  has  been  carried  to  nearly  half  the  stroke  of  the  small  cylinder, 


THE  ALSA  TIAN  EXPERIMENTS,  K  Tf.  249 


without  preventing  the  evaporation  of  10  per  cent,  of  the  fluid  originally 
condensed,  and  a  rapid  augmentation  of  the  internal  heat  of  steam,  22.29  c. 
for  C,  and  22.35  D.  (U0 — E^).  We  see  also  that  during  expansion  in  the 
large  cylinder  a  portion  of  the  vapor,  existing  at  the  end  of  the  stroke, 
in  the  small  cylinder,  has  been  condensed  about  5  percent.,  and  the  in- 
ternal heat  of  the  steam  (Uf—UJ  diminished  23.53  c.  C,  and  25.59  c.  D. 

The  number  of  calories  returned  by  the  internal  heat  during  the  stroke 
of  the  large  piston  is  nearly  the  same  as  the  work  of  expansion,  25  c.  in 
the  large  cylinder;  we  could  then  conclude  that  the  steam  jacket  has  done 
nothing  in  this  second  expansion,  in  a  word,  does  not  perform  its  office. 

Arriving  at  this  conclusion  will  be  denying  one  of  the  elementary  prin- 
ciples of  physics,  for  we  know  that  the  greater  the  difference  of  tempera- 
tures the  more  energetic  the  transfers  of  heat.  During  the  stroke  of  the 
large  piston  the  temperature  of  the  steam  in  the  jackets  is  much  higher 
than  that  of  the  steam  in  the  cylinders,  it  is  then  during  this  period  that  the 
transfer  of  heat  should  be  best  made — that  the  jacket  should  furnish  more; 
this  is  really  what  takes  place. 

We  will  show  later  in  treating  of  expansion  how  the  passage  of  calo- 
ries is  made,  and  what  is  their  occupation;  we  shall  see  that  this  pheno- 
menon, which  appears  at  first  to  be  entirely  abnormal,  explains  itself 
naturally;  we  shall  see  it  become  a  very  simple  consequence  of  the  princi- 
ple of  the  transmission  of  heat  which  it  seems  at  first  to  contradict. 

We  give  then,  to  terminate  the  series  of  analyses,  the  two  experiments 
E  and  F,  made  with  expansions  28  and  25.  We  regret  that  we  cannot  join 
thereto  the  analytical  story  of  the  engine  at  St.  Eemy.  Its  consumption 
checks  within  3  per  cent,  nearly,  and  it  agrees  closely  with  the  Malmers- 
pach  engine,  but  it  lacks  the  exact  elements  necessary  in  the  indicator 
diagrams. 

MALMERSPACH  ENGINE,   EXPERIMENT  E.,  143  H.  P.;   EXPANSION,  28. 

Account  of  heat,  etc.,  per  stroke: 

Weight  of  fluid  in  small  cylinder 0.3679  k. 

"      dry  steam  at  cut-off. .  0.2214  k. 


water  (40  per  cent.) 0.1465  k. 

"    entrained..  0.0200k. 


;    condensed 0.1265  k. 

Heat  given  to  iron 63.08  c. 

Weight  of  fluid  in  large  cylinder 0.3679  k. 

*'          dry  steam  at  end  of  stroke ..  0.3030k. 


water                                     (7.6  per  cent.) 0.0640  k. 

Internal  heat  at  end  of  admission,  U0 157.44  c. 

"             "        "         stroke,   U^ 183.32  c. 

U«—  U,..  25.88  c. 


250  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


Heat  furnished  by  jacket 16.09  c. 

"  "  iron  above..  63.08  c. 


Total  heat  furnished  during  expansion 53.29  c. 

Heat  in  total  work    "            "              "           29.35  c. 

"    "    external  radiation 4.60  c. 

Re 19.34  c. 

Relatively  to  entire  heat  furnished       '     -  =  7.8  per  cent. 

—  H  l.  I  ( 

Check  on  Re: 

Internal  heat  at  end  of  stroke,  Uv 183.32  c. 

Back  pressure  work 6.63  c. 

Heat  retained  in  condensed  steam. .  6.99  c. 


182.96  c. 

Heat  gained  by  injection  water ;    198.21  c. 

Re ! 15.25  c. 

Differing  from  the  other  "^t^Jf'"  =  L6  Per  cent- 

CTg  at  end  of  stroke  small  cylinder: 

Weight  of  fluid 0.3679  k. 

"        "  steam  end  of  stroke. .  0.2976  k. 


"  water    '                       (19.1  per  cent.) 0.0702  k. 

Internal  heat          "           "        Uz 186.81  c. 

MALMERSPACH  ENGINE,    EXPERIMENT   F.,  149  H.    P.;   EXPANSION  25. 

Account  of  heat,  etc.,  per  stroke: 

Weight  of  fluid  in  small  cylinder 0.3862  k. 

dry  steam  at  cut-off 0.2471  k. 

"           water        "        "       (36.1  per  cent.) 0.1391  k. 

"    entrained 0.0210  k. 

"               "    condensed 0.1181  k. 

Heat  given  to  iron 58.83  c. 

Weight  of  fluid  in  large  cylinder 0.3862  k. 

dry  steam  at  end  of  stroke €.3180  k. 

water               "               "      (17.8  per  cent.) 0.0682k. 

Internal  heat  at  cut-off,  Z70 172.10  c. 

"     "  end  of  stroke,  t/i 192.45  c. 

U0—  U, —20.35  c. 

Heat  furnished  by  jacket 17.38  c. 

"            "                iron  above..  58.83  c. 


Total  heat  furnished  during  expansion 55.86  c. 


THE  ALSATIAN  EXPERIMENTS,  ETC.  251 

Heat  furnished  during  external  radiation 4.60  c. 

absorbed  by  total  work 29.93  c. 

RC 21.33  c. 

91   *¥\ 

being  _-   —  =  8.2  per  cent,  of  entire  heat  per  stroke. 
259.53 

Check  on  Re: 

Internal  heat  at  end  of  stroke,  £7^ 192.45  c. 

Back  pressure  work 346.43  c. 

Heat  retained  after  condensation -  7.50  c. 

191.38  c. 
"      gained  by  injection  water 210.33  c. 

Re 18.95  c. 

Differing    21.33—18.95  =o.9percent. 
2o9.53 

Weight  of  fluid  in  small  cylinder 0.3862  k. 

"          dry  steam  at  end  of  stroke 0.3147  k. 

"  water  (18.6  per  cent.) 0.0715  k. 

Internal  heat,  Z72 197.46  c. 

These  two  experiments  E  and  F,  give  results  which  accord  perfectly 
with  expansions  28  and  25.  We  should  also  note  in  order  the  profound 
modifications  to  which  the  steam  is  submitted  when  the  expansion  is 
changed  from  13  to  28.  The  internal  heat  which  in  C  diminishes  1.24  c. 
during  the  expansion,  changes  to  an  increase  of  25.88  c.  for  E,  while  for  D 
and  F  there  is  for  one  a  diminution  of  3.24  c.,  and  for  the  other  an  acces- 
sion of  20.35  c.  between  expansion  13  and  25. 

INFLUENCE  OF  VARIABLE  EXPANSIONS  UPON  THE  WORKING  OF  STEAM  IN 
"WOOLF"  ENGINES  — THEIR  UTILITY  FROM  THE  POINT  OF  VIEW  OF  CON- 
SUMPTION. 

The  exposition  of  the  very  complex  phenomena  which  absorb  us,  the 
study  of  which  should  be  made  as  clear  and  as  easily  grasped  as  possible 
induces  us  to  give  in  Table  III.,  page  254,  a  summary  of  the  principal 
results  which  form  the  basis  of  our  discussion. 

The  action  of  the  iron  upon  the  fluid  which  it  incloses  is  so  well  estab- 
lished, and  the  result  of  Hirn's  labors  on  heat  engines  is  such  that  it 
naturally  follows  that  variable  expansions  modify  the  nature  even  of  the 
work  of  steam.  We  introduce  into  the  cylinders  different  weights  of 
steam,  different  quantities  of  heat,  therefore  it  is  not  astonishing  to  see 
during  expansion  variations  in  the  direction  and  amount  of  the  changes 
of  heat.  But  that  which  should  be  useful  in  practice  is  the  experimental 
determination  of  these  changes,  followed  by  the  results  of  their  analysis, 
and  their  justification.  We  shall  fall  perchance  on  facts  at  first  inadmis- 
sible like  those  we  found  for  expansion  13,  and  find  the  natural  explana- 
tion in  the  most  profound  study  of  the  phenomenon,  a  purely  physical 
study. 


252  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

The  paradoxical  fact  which  we  will  recall  is  presented  then  in  experi- 
ments C  and  D  upon  each  of  the  Malmerspach  engines  working  with 
expansion  13,  and  with  full  pressure  more  than  one-half  of  the  stroke  in 
the  small  cylinder.  During  the  expansion  in  the  large  cylinder  a  portion 
of  the  steam  existing  at  the  end  of  the  stroke  of  the  small  piston  is  con- 
densed— Experiment  C.,  4.8  per  cent.;  Experiment  D.,  5.2  per  cent.  The 
internal  heat  has  diminished  Z72—  U^=  +  23.53c.  and  25.59.  But  the  work 
of  expansion  in  the  large  cylinder  has  demanded  and  absorbed  24.9  c.  and 
25  c.,  that  is  to  say,  nearly  the  same  amounts  for  this  period  of  work. 
There  was  no  heat  furnished  from  outside;  the  jacket  appears  to  have 
yielded  nothing;  was  it  not  working  during  this  period  of  expansion? 

This  hypothesis  is  inadmissible,  for  we  have  seen  that  it  contradicts  a 
well-known  principle,  of  physics  relative  to  the  transmission  of  heat;  the 
exchange  of  heat  across  the  sides  of  the  cylinder  should  be  more  rapid 
with  the  greatest  difference  of  temperature  between  the  two  surfaces, 
for  one  of  them  is  in  contact  with  the  jacket  steam  at  boiler  pressure, 
and  the  other  possesses  the  temperature  of  the  cylinder  steam  at  a  much 
lower  pressure.  We  would  remark  that  the  difference  of  temperature  is 
not  the  only  factor  which  can  accelerate  this  transfer;  the  layer  of  water, 
which  covers  the  internal  surface  has  also  its  influence;  it  augments  the 
rapidity  with  which  heat  is  brought  to  the  inner  surface;  it  provokes  a 
proportionally  greater  action  in  the  jacket,  as  we  will  prove  by  the  figures 
of  Table  III. 

How  can  it  be,  then,  since  the  jacket  is  in  the  best  possible  condition 
to  furnish  heat,  that  it  appears  to  be  inactive?  This  apparent  anomaly 
has  a  very  simple  cause — the  action  of  the  surfaces  at  the  commencement 
of  the  stroke  of  the  large  piston. 

I  established  in  my  paper  of  1878  that  at  the  first  tenth  of  the  stroke 
of  the  large  piston,  a  moment  when  the  dry  steam  is  nearly  equally  divided 
between  the  small  and  large  cylinders,  there  is  one-half  at  least  of  the 
fluid  deposited  as  water  upon  the  walls  of  the  large  cylinder;  if  we  mark, 
then,  that  at  the  end  of  the  first  tenth  of  the  stroke  of  the  large  piston  the 
large  cylinder  contains  more  water  than  steam,  that  is,  that  the  first  part 
of  this  stroke  the  condensation  has  been  very  considerable,  while  the 
cooling  due  the  condenser  has  been  only  1.3  per  cent.  loss. 

The  same  fact  is  presented  for  experiments  0  and  D  in  stronger  pro- 
portions yet;  since  by  the  cooling  due  the  condenser  the  heat  taken  from 
the  iron  during  exhaust  is  8.3  and  9.9.  It  is  upon  this  water  which  covers 
the  surface  that  the  jacket  acts,  and  since  it  cannot  evaporate  a  sufficient 
quantity,  the  internal  heat  at  the  end  of  the  stroke  is  less  than  at  the  end 
of  the  stroke  of  the  small  piston.  Such  is  the  particular  circumstance 
which  the  five  experiments  made  upon  the  coupled  engines  at  Malmers- 
pach present  to  us;  it  is  not  the  first  time  we  have  had  occasion  to  remark 
it.  I  have  already  noted  it  in  the  experiments  made  on  the  Munster  en- 
gines, 1876,  working  with  little  compression  in  the  clearance  spaces. 

Let  us  indicate  the  modifications  which  a  variable  expansion  brings 
to  the  transformation  of  steam  and  to  the  action  of  the  jacket. 


THE  AL8A  TIAN  EXPERIMENTS,  ETC.  253 


The  three  experiments,  B,  C  and  E,  the  first  the  result  of  a  very  slight 
expansion  in  the  small  cylinder  where  the  steam  has  been  admitted 
nearly  all  the  stroke,  with  a  total  expansion  of  6;  the  Indicated  H.  P.  only 
reaches  201.  To  do  this  feeble  work  the  steam  pressure  had  to  be  throt- 
tled, for  we  have  with  thirteen  expansions  and  full  pressure,  a  work  of  215 
H.  P.,  a  greater  load  in  spite  of  the  less  introduction. 

In  these  conditions  the  weight  of  steam  condensed  during  admission 
is  small,  12.8  per  cent.,  less  the  water  carried,  over  5  per  cent.  =  7.8  per 
cent,  deposited  upon  the  surface.  The  jacket  yields  proportionately  less 
heat,  for  it  only  condenses  5  per  cent,  of  the  steam  brought  to  the  engine. 
We  remark  that  in  spite  of  the  condensation  which  took  place  at  the  first 
stroke  of  the  large  piston,  the  proportions  of  water  are  within  1.3  percent, 
the  same  at  the  beginning  and  end  of  the  expansion,  and  that  the  cooling 
due  the  condenser  is  small  enough,  2.1  per  cent,  of  the  entire  heat  brought 
the  engine.  In  spite  of  these  conditions,  which  appear  advantageous 
enough,  the  consumption  per  total  H.  P.  is  7,404  k.,  while  those  of  C  and 
E  are  6,878  k.,  and  6,731  k.,  that  is  to  say,  by  7  and  9  per  cent. 

Is  this  the  gain  realized  by  the  expansion?    This  we  shall  see. 

Experiment  C,  with  introduction  of  half  stroke  in  the  small  cylinder, 
presents  a  condensation  of  23.7  —  5  =  18.7  per  cent,  during  the  admis- 
sion, but  the  proportion  of  water  which  is  found  is  partly  evaporated 

Passing  to  the  results  of  experiment  E,  expansion  28,  this  modification 
is  much  more  marked.  The  proportion  of  water  at  the  end  of  an  intro- 
duction of  £  stroke  of  small  cylinder  is  40  per  cent.,  and  21  per  cent, 
evaporates  during  the  first  expansion,  and  the  internal  heat  increases 
29.37  c.;  in  short,  we  see  that  as  the  expansion  in  the  small  cylinder  is 
increased  the  transfers  of  heat  are  increased. 

On  the  other  hand,  the  action  in  the  large  cylinder  follows  another 
law.  We  have  seen,  that  with  nearly  full  stroke  introduction  in  the  small 
cylinder,  experiment  B,  the  internal  heat  remains  nearly  stationary, 
diminishing  by  only  7.17  c.,  between  the.ends  of  the  stroke  of  the  small  and 
large  pistons.  The  same  fact  is  found  in  experiment  E,  28  expansions. 
But  we  have  seen  above  that  the  intermediate  experiments  C  and  D  show 
us  a  considerable  fall  of  internal  heat,  a  fall  sufficient  to  furnish  to  the 
work  of  expansion  the  number  of  calories  which  it  requires.  Here  there 
is,  then,  as  in  the  small  cylinder,  an  increase  in  the  transfers  of  heat  from 
experiments  B  to  C,  but  a  decrease  follows  the  minimum,  which  appears 
toward  expansion  13,  to  which  is  due  that  the  internal  heat  t/i  is  increased 
relatively  to  the  final  internal  heat  U.2  of  the  small  cylinder. 

By  considering  only  the  phenomena  of  the  total  expansion  from  the 
moment  that  it  commences  in  the  small  cylinder  to  the  end  of  the  stroke 
in  the  large  cylinder,  we  see  that  the  differences  of  internal  heat  are  con- 
tinually reversed;  this  shows  that  the  transfers  of  heat  are  greater  and 
greater  as  the  expansion  is  increased.  Thus  for  experiment  B  the  final 
internal  heat  Ul  is  7.17  c.  less  than  U0  at  the  end  of  admission;  for  experi- 
ment C  this  difference  is  only  1.24  c.;  while  for  experiment  E  the  differ- 
ence is  reversed,  and  the  final  internal  heat  is  25.88  c.  larger  than  at  the 


254 


STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


1 

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d 

on      o      10 

00  tO  rH  rH  •«»(         t-  t-  rH  O5  <M  CM  W5  -*  CO 

rH  rH          rH          CO                        <M  rH  rH          <M  CS)  CO 

H 

JH          CO          OS                                      OOt-OJ-* 
t-  «O  «  t-  O         >O  O  rH  <O  00  CO  M<  CO  CO 

co  co  to  co  co  <M  o  ko  oo"  o  O5  t-'  id  01  co'  oi  t^ 

::::::::::::«        :  : 

PER  SINGLE  STROKE. 

1     !  ;    !-•  ii 

ii-l-i      ••«     i; 

:  fe  :S  •  g           :  :^bb  ;  : 

of  expansions  
cated  horse-power  on  pistons  
steam  per  hour  per  total  horse-power,  kilo 
£  pressure  work,  per  cent,  of  total  work.  .  . 
steam  per  hour  per  indicated  horse-power, 
tianical  efficiency,  percent  
steam  per  hour  per  net  horse-  power,  kilog 
cent,  priming  or  water  entrained  
steam  condensed  in  jackets  
water  in  steam  at  cut-off  
end  small  cylinder 
end  large  cylinder 
age  of  internal  heat  during  expansion  Uo— 
"  in  small  cylinder  77o— 

in  large  cylinder  17%— 
JKC  or  cooling  due  condenser  in  calories  
Re  in  per  cent,  total  heat  brought  to  engine.  .  . 

lUIHril      i 

THE  ALSATIAN  EXPERIMENTS,  ETC.  255 

end  of  admission.  The  qualities  of  heat  furnished  by  the  jacket,  the 
proportions  of  steam  condensed  in  the  small  cylinder  during  admission, 
which  transforms  the  inner  surface  of  the  cylinder  into  a  reservoir  of  heat, 
and  the  internal  heat,  all  these  values  are  intimately  connected  together, 
as  we  have  already  said  many  times:  they  depend  the  one  on  the  other; 
and  are  in  some  sort  the  various  manifestations  of  the  same  thing.  We 
also  see  them  changing  in  kind  the  condensation  in  the  jacket  and  small 
cylinder  during  admission;  increase  with  expansion,  furnishing  thus 
more  heat  in  proportion  than  is  measured  by  the  expansion  and  consider- 
ably more. 

This  law  appears  to  be  general  in  "Woolf"  engines,  not  only  with 
variable  expansions,  but  for  fixed  expansions  and  variable  powers  obtained 
by  throttling  the  steam.  The  experiments  upon  the  "Munster"  engine 
show  us  that  with  185  H.  P.  the  final  internal  heat  U^  is  31.89  c.  more  than 
the  initial  internal  heat  U0  at  the  end  of  the  admission,  while  this  differ- 
ence is  only  17.40  c.  for  the  experiment  with  347  H.  P.  Meanwhile  exam- 
ining more  closely  the  figures  of  the  two  series  of  experiments  at 
Malmerspach  and  Munster,  we  discover  one  point  which  merits  being 
brought  into  light.  The  differences  U0 — Ut  are  close  together  for  experi- 
ments I.  and  II.,— 17.40  c.  and  16.58  c.,  more  alike  than  B  and  C,  7.17  c.  and 
1.24  c.,  which  differ  much  from  E,  25.88  c.  This  leads  us  to  believe  that 
in  the  limits  of  expansion  and  throttling  of  experiments  I.,  II.,  B,  C,  the 
differences  of  internal  heat  remain  nearly  stationary;  they  only  commence 
to  increase  rapidly  when  we  go  beyond  13  expansions  and  throttle  below 
267  H.  P.  of  experiment  II. 

Finally  we  see  for  all  the  "Munster"  eperiments  of  1877  the  final 
internal  heat  U^  is  greater  than  the  initial  internal  heat  U0.  If  this  fact  is 
the  reverse  of  what  was  produced  upon  the  same  engine  in  1876,  it  is  that 
at  that  time  the  engine  was  differently  regulated,  the  compression  in  the 
clearance  space  being  much  less.  The  increase  of  compression  diminished 
greatly  the  lead  influence  of  the  clearance.  This  realized  an  economy 
and  the  result  betrays  itself  by  an  increase  in  the  final  internal  heat.  It  is 
not  necessary  to  believe  that  this  is  always  the  characteristic  sign  of  a 
better  working  of  the  engine.  We  have  in  effect  experiments  C  and  E,  of 
which  the  consumptions  vary  only  2.1  per  cent,  when  the  differences  of 
internal  heat  U0 — U±  are  1.24  c.,  and  —  25.88  c.  On  the  other  hand,  experi- 
ments I.  and  II.  give  U0  —  U^—  —  17.40  c.  and  16.58  c. .  and  meanwhile  the 
consumptions  vary  2.4  per  cent.,  the  least  being  for  experiment  II. 
throttled  to  267  H.  P. 

Summing  the  effects  of  a  greater  total  expansion,  commencing  in  the 
small  cylinder  and  placing  parallel  to  them  the  effects  of  the  same  kind 
produced  by  throttling,  reducing  the  indicated  work  in  the  same  propor- 
tion that  the  change  of  expansion  did,  the  best  experiments  are  C  and  E, 
expansions  13  and  28,  and  experiments  II.  and  III.,  with  the  same  expan- 
sion 7.  The  indicated  horse-powers  are  nearly  in  the  same  ratio, 
215  -  267  , 


256  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

"When  the  expansion  changes  from  13  to  28  the  condensation  in  the 
small  cylinder  during  admission  increases  from  23  to  40  per  cent.;  the 
heat  given  to  the  iron  is  increased.  The  jacket  also  gives  a  little  more 
heat,  but  the  greater  part  of  this  heat  is  restored  in  the  small  cylinder 
itself.  It  furnishes  there  more  heat  than  is  needed  for  the  work  of  expan- 
sion, for  the  evaporation  of  10  and  21  per  cent,  of  the  water  deposited 
upon  the  surface.  This  is  proved  by  the  increase  of  internal  heat  by  22 
and  29  c.  at  the  end  of  the  stroke  of  the  small  piston.  In  the  same  circum- 
stances, throttling  with  nearly  full  admission  in  the  small  cylinder, 
experiments  II.  and  III.,  the  communication  between  cylinder  and  boiler 
is  open  also.  The  proportions  of  steam  condensed  only  vary  from  14  to 
21  per  cent.,  which  show  a  very  different  kind  of  working.  The  steam 
passes  then  to  the  large  cylinder;  it  is  in  this  that  the  transfers  of  heat 
are  found  which  did  not  take  place  in  the  small  cylinder.  The  internal 
heat  is  increased  during  the  expansion  16  and  31  calories;  9  and  14  per 
cent,  of  the  water  is  evaporated.  On  the  other  hand,  with  13  and  28 
expansions,  commenced  with  cut-offs  at  one-half  and  one- fifth  in  the  small 
cylinder,  the  reverse  action  took  place.  The  energetic  changes  are  less 
in  the  large  cylinder  than  in  the  small  cylinder.  This  is  a  fact  which  will 
serve  us  later  in  comparing  single  and  double  cylinder  engines. 

Experiment  B  seems  to  contradict  this  law,  for  the  internal  heat 
diminishes  7  calories  from  the  beginning  to  the  end  of  the  expansion,  and 
the  proportions  of  water  are  nearly  the  same,  12  and  11  per  cent.  This  is 
due  to  two  causes,  the  influence  of  a  distribution  with  very  little  com- 
pression, and  the  less  effect  of  the  jacket,  where  there  is  only  5  per  cent, 
of  the  weight  of  the  steam  condensed;  but  it  is  none  the  less  true,  that  the 
heat  furnished  by  the  jacket  has  been  during  the  expansion  in  the  large 
cylinder.  Before  attacking  the  question  from  the  practical  industrial  side 
let  us  seek  to  render  an  account  of  the  advantages  of  expansion,  consid- 
ering only  the  work  of  the  steam;  that  is  to  say,  abstracting  imperfections 
of  vacuum  and  frictions  of  the  engine. 

In  principle,  theory  has  conducted  M.  G.  Zeuner  to  recommend  very 
prolonged  expansions;  M.  G.  A.  Hirn,  on  the  contrary,  considering  the 
practical  conditions  imposed  on  the  engine,  adopts  moderate  expansions. 
We  shall  see  that  these  two  opinions  which  appear  contradictory  are  both 
sanctioned  by  our  experimental  researches  when  properly  analyzed.  The 
work  of  M.  Zeuner  supposed  that  the  cylinder  was  non-conducting,  and 
the  closed  cycle  perfect,  but  it  is  clear  that  the  cycle  is  interrupted  by  the 
conditions  in  which  we  place  our  "Woolf "  engines.  We  should  naturally 
expect  to  see  the  benefits  of  expansion  considerably  diminished  by  the 
transfers  of  heat  to  the  internal  surfaces;  but  the  difference  is  great  enough 
to  allow  us  to  affirm  the  law. 

Commencing  by  comparing  the  cost  per  total  H.  P.  of  experiments  I., 
II.,  III.,  C  and  E,  experiment  I.,  347  H.  P.,  expansion  7,  has  been  made 
with  an  initial  pressure  near  that  of  C  and  E,  but  it  is  experiment  II., 
made  with  a  lower  pressure,  which  presents  the  minimum  cost,  6.945  k. 
This  is  due  to  some  particular  circumstance  which  we  have  not  been  able 


THE  AL  SA  TIAN  EXPERIMENTS,  ETC.  257 


to  bring  out;*  and  which  causes  the  cooling  due  the  condenser  to  be  least 
for  experiment  I.,  while  to  compensate  this  action  we  take  for  the  con- 
sumption for  7  expansions  the  mean  of  I.  and  II.,  7.028  k.  The  cut-offs  for 
expansions  7,  13  and  28  are  in  the  ratio  of  1,  ^  and  J;  the  costs  are  7.028  k., 
6.878k.;  and  7.731k.,  a  decrease  of  2.2  per  cent.;  or  an  expansion  four 
times  as  great  procures  4.4  per  cent.  gain.  The  law  of  M.  Zeuner  is  then 
found  verified  experimentally  in  "Woolf "  engines.  It  is  to  be  noted  that 
the  disturbing  effect  of  the  surfaces  does  not  reverse  this  law,  for  in  the 
method  used  to  determine  the  cost  this  influence  is  fully  accounted  for. 
The  cost  for  experiment  III.,  185  H.  P.,  7  expansions,  is  5  per  cent,  inferior 
to  that  of  I.,  II.  Whence  we  conclude  that  it  should  have  a  marked  advan- 
vantage  of  about  10  per  cent,  in  replacing  by  more  expansion  a  too  great 
lowering  of  initial  pressure. 

We  have  left  to  one  side  experiment  B,  made  with  the  same  engine  as 
C  and  E,  for  two  motives,  which  appeared  to  us  ought  to  exclude  it;  in  the 
first  place  the  jacket  did  not  yield  enough  heat.  And  then  the  valves  are 
set  with  a  compression  not  sufficient  to  help  the  clearance.  But  every- 
body knows  that  one  of  the  effects  of  a  prolonged  expansion  is  to  exten- 
uate in  part  the  pernicious  effect  of  the  considerable  waste  spaces  of  the 
"Woolf"  engine. 

The  cost  of  a  net  H.  P.  brings  us  the  modifications  of  the  more  or  less 
perfect  vacuum  which  falsifies  the  preceding  law;  thus  experiments  I.  and 
II.  differ  in  reverse  order  1.4  per  cent.,  and  C  and  E,  which  vary  1.5  per 
cent. 

Finally  the  cost  of  a  net  H.  P.,  upon  which  the  combined  effects  of 
poor  vacuum  and  friction  give  the  following  results:  Experiment  I.,  9.864 
k.;  II.,  10.357k.;  III.,  12.411  k.;  C,  9.465k.;  E,  10.019  k.  The  least  is  exper- 
iment C,  expansion  13;  it  only  varies  5£  per  cent,  from  E,  expansion  28, 
and  4  per  cent,  from  I,  expansion  7,  full  pressure.  This  justifies  the  prop- 
osition of  M.  Him.  There  remains  to  calculate  the  dimensions  to  be  given 
to  engines  and  the  frictions  which  result,  the  foreknowledge  of  the  inter- 
rupted cycle  and  the  moderate  expansion.  In  a  word  he  says:  "For 
reasons  of  practical  fact  the  steam  engine  with  broken  cycle  and 
moderate  expansion  works  better,  notwithstanding  its  faults,  than  the  en- 
gine working  with  the  perfect  cycle,"  without  regard  to  first  cost. 

Experiment  III.,  185  H.  P.,  expansion  7,  pressure  much  reduced,  differs 
24  per  cent,  from  the  corresponding  experiment,  E,  expansion  28,  full 
pressure.  This  difference  is  due  to  the  vacuum  and  friction.  If  the  hori- 
zontal engine  occupies  the  last  rank,  it  owes  it  to  the  small  compression, 
its  vacuum  and  frictions.  Its  inferiority  is  only  2  per  cent,  relatively  to 
the  corresponding  experiment  II.  and  B,  and  6  per  cent,  referred  to  the 
experiment  with  greatest  power,  I.,  347  H.  P. 

The  practical  consequences  of  these  collected  researches  upon  the 
"Woolf"  engine  may  be  stated  thus: 

1.  From  the  total  point  of  view,  considering  only  the  best  utilization 
of  the  heat  brought  to  the  engine,  we  can  reduce  the  maximum  work  with 
5  kilos,  pressure.  For  example  (70  pounds),  expansion  7  to  i,  by 


258  STEAM  USING;  OH,  STEAM  ENGINE  PRACTICE. 

diminishing  the  initial  pressure,  and  there  results  a  loss  of  5  per  cent,  of 
the  cost  of  a  total  H.  P.;  while  by  reducing  the  introduction  in  the  small 
cylinder,  we  can  gain  4£  per  cent,  of  the  same  cost. 

2.  When  one  is  obliged  to  reduce  the  work  one-half,  whether  because 
of  a  change  of  load  or  because  used  with  water  power,  we  can  make  a 
practical  gain  of  10  per  cent,  at  least  by  replacing  the  throttle  by  a  varia- 
ble cut-off  in  the  small  cylinder.     We  suppose  it  well  understood  that  the 
back  pressure  work  remains  the  same  in  the  two  cases.     The  friction  is 
naturally  the  same,  since  the  work  is  the  same. 

3.  The  engine  working  near  its  full  load,  it  is  possible  to  vary  the 
work  10  per  cent,  more  or  less,  without  any  notable  change  in  the  eco- 
nomic re'gime  due  to  expansion  or  change  of  pressure.     There  follows  the 
disposition  we  have  already  remarked;  an  expansion  variable  by  hand  and  a 
governor  throttle  valve,  which  will  answer  all  requirements,  and  is  the 
most  simple  and  durable. 

INFLUENCE  OF  EXPANSION  IN  SINGLE   CYLINDEE  ENGINES. 

We  proceed  with  this  study  as  we  did  with  the  "Woolf"  engines, 
checking  first  the  consumption  of  the  different  experiments  of  which  we 
make  use.  These  experiments  are  upon  four  valve  engines  with  and  with- 
out jackets.  They  consist  first  of  experiments  made  upon  a  horizontal 
"Corliss"  by  the  Mechanical  Committee  of  the  Industrial  Society  in  April 
and  May,  1878. 

The  experimental  process  is  that  of  M.  Hirn  often  described  in  our 
Bulletins,  and  the  direct  results  of  observations  are  given  in  that  for  Dec., 
1878.  I  have  checked  and  analyzed  them,  and  added  the  experiments 
made  in  1873  and  1875,  upon  the  vertical  engine  with  four  valves  of  M. 
Hirn,  without  a  jacket,  and  with  and  without  superheating;  it  was  also 
tried  with  a  brake  in  1865  by  the  Mechanical  Committee.  We  will  com- 
mence with  the  results  of  the  "Corliss:" 


Corliss  Engine  by  Berger,  Andre  &  Co. 

Tried  with  brake  by  the  Mechanical  Committee;  check  on  direct  con- 
sumption. 

I.— Indicated  on  piston 105      H.  P. 

Revolutions  per  minute 50.41. 

Net  on  brake 92      H.  P. 

Mechanical  efficiency,  per  cent 88 

Back  pressure  work  in  per  cent,  total  work 10 

(2.1  Tbs.)     0.148  k. 

Expansion 11 

(Boiler  pressure  68  Ibs.  above  atmosphere.) 


THE  ALSATIAN  EXPERIMENTS,  ETC.  25S 

Per  single  stroke : 

Heat  brought  by  dry  steam 0.1306  k.  x  654.24  c.  =  85.44  c. 

"        "    water  entrained 0.0043  k.  x  158.18  c.  =    0.68  c. 

"    steam  to  jacket..  ...  .0.0094  k.  x  496.06  c.  =    4.66  c. 

"         to  engine 90.78  c. 

"      kept  to  condenser. 0.1349  k.  x  23.5  c.  =    3.17  c. 


expended,  Q0 87.61  c. 

"      gained  by  injection  water,  Ql 5.4304  k.  x  13.3  c.  =  72.22  c. 

15.39  c. 

"      in  work  done 11.03  c. 

"      radiated 1.50  c. 

12.53  c. 

Error,  15-39-12'53=  3.1  per  cent. 
90.78 

Total  heat  is  90.78  c.,  it  represents: 

Dry  steam  per  stroke 90-78    =0.1387  k. 

6o4.24 

"      hour  per  total  H.  P 7.188  k. 

ind.  H.  P 7.983  k. 

net    H.  P 9.071  k. 

II.— Indicated  on  pistons 137      H.P. 

Revolutions  per  minute 51.12 

Net  H.  P 135 

Mechanical  efficiency,  per  cent 91 

Back  pressure  work  in  per  cent,  total  work 8.8 

(2^  Ibs.)  —0.169  k. 

Expansion 8 

(Boiler  pressure  66  Ibs.  above  atmosphere). 

Heat  brought  by  dry  steam 0.1678  k.  x  653.82  c.  =  109.71  c. 

"    entrained  water 0.0075  k.  x  156.74  c.  =      1.16  c. 

"    jacket .  .0.0112  k.  x  497.08  c.  =      5.57  c. 


Total. 116.44  c. 

Heat  retained  to  condenser. .  .  .0.1752  k.  x  27.65  c.  =      4.84  c. 


Q0  .........................................................  111.60  c. 

Heat  gained  by  injection  water  .............  9.534  k.  x  17.45  c.  =     93.18  c. 

o—     .......................................................     18.42  c. 


Heat  in  work  done  ........................................  14.25  c. 

"      "  external  radiation  .................  ...............  1.50  c. 

-     15.75  c. 


Error,  ~'      =  2.3  per  cent. 


260  STEAM  USING;  Oil,  STEAM  ENGINE  PRACTICE. 

Heat  per  stroke,  116.44  represents: 

Dry  steam  per  stroke  ...................................  116:44L  =    0.1781  k. 

653.82 

"    hour  per  total  H.  P  ...................    ..........  7.236  k. 

"      "    ind.   H.P  ............................     7.939k. 

"        "  "        "       "net     H.  P  ...........................     8.724  k. 

III.—  Indicated  on  piston  ..............  .  ......  .............  158      H.  P. 

Revolutions  per  minute  ...........  ............................  49.54 

Net  on  brake  ..................................................  142 

Mechanical  efficiency,  per  cent  ................................  92 

Back  pressure  work  in  per  cent,  of  total  work  .................     8.1 

..........................................  (2.6  Ibs.)     0.184k. 

Expansion  .....................................................     6 

(Boiler  pressure  68  Ibs.  above  atmosphere.) 
Heat  brought  by  dry  steam  ......  .  .........  0.2015  k.  x  654.24  c.  =  131.83  c. 

"  entrained  water  ..........  0.0112  k.  x  158.18  c.  =      1.77  c. 

"  to  jacket  ...................  0.0114  k.  x  0.0114  c.  =      5.65  c. 

Total  .......................................................  139.25  c. 

Heat  retained  by  condenser  ..................  0.2127  k.  x  29.57  c.  =     6.29  c. 

#0  ............................................................  132.96  c. 

Heat  gained  by  injection  water  Ql  ...........  5.7334  k.  x  19.47  c.  =  111.63  c. 

Q0—Ql  .............................  ..........................   21.33  c. 

Heat  in  work  done  .......................................  .  16.99  c. 

"     "    external  radiation  ................................  1.50  c. 

-  18.49  c. 


Error,     -JrL  =  2.4  per  cent. 

Heat  per  single  stroke  =  139.25  represents 
Dry  steam  per  stroke  ...................................         o     =  °'2128  k< 

004.^4 

"    hour  per  total  H.  P  ...............................  7.307  k. 

"         "  "      "      ind.   H.  P  ..............................  7.955  k. 

"          "        "       "       "      net    H.P  ............................  ...8.646k. 

These  three  experiments  check  within  3  per  cent.,  a  very  satisfactory 
result  but,  let  us  add,  one  difficult  enough  to  obtain. 

It  is  essential,  as  we  have  seen  from  a  long  practical  experience  in 
these  researches,  to  attend  to  the  most  minute  precautions  to  attain  results 
which  check  to  about  1  per  cent.,  and  we  consider  as  purely  accidental, 
circumstances  which  give  closer  figures,  and  believe  the  attempt  to  get 
them  an  illusion. 

The  consumptions  of  the  "Corliss"  engine  with  expansion  of  6,  8,  and 
11,  show  us  the  limited  influence  of  expansion  upon  the  cost.  I  have 
already  had  occasion  to  note  this  fact  when  the  "Woolf  "  engines  were  in 
question.  There  results  from  this  that  within  the  wide  limits  where  we 


THE  ALSA TIAN  EXPERIMENTS,  ETC.  261 


have  operated,  and  for  jacketed  engines,  the  intrinsic  work  of  the  steam  is 
scarcely  influenced  by  a  more  or  less  prolonged  expansion,  this  being 
defined  by  the  cost  of  a  total  H.  P. 

The  "Woolf"  engines  gained  4.5  per  cent,  by  change  from  7  to  28  ex- 
pansions. The  "Corliss"  gains  1.6  per  cent,  by  change  from  6  to  11. 

On  the  other  hand,  for  the  "Corliss"  as  well  as  the  "Woolf,"  the  Differ- 
ences which  exist  in  cost  change  sign  when  we  pass  from  the  total  work  to 
the  indicated  work  in  which  the  back  pressure  makes  itself  felt;  these 
differences  are  still  more  increased  when  we  take  the  cost  of  a  net  horse- 
power, that  is  to  say,  the  industrial  consumption,  which  shows  us  that 
expansion  6  is  4.5  per  cent,  better  than  11  for  the  "Corliss"  engines,  and 
for  "Woolf"  engines  expansion  13  is  5.5  per  cent,  better  than  28. 

That  which  we  have  noted  concerns  only  jacketed  engines.  Does  ex- 
pansion act  differently  without  this  adjunct? 

The  experiments  made  upon  the  vertical  engine  of  M.  Hirn  will 
show  us. 

Hirn  Engine. 

Saturated  steam,  variable  expansions.     Check  on  consumption. 

I.     Indicated  on  pistons 107     H.  P. 

Revolutions  per  minute 30.41 

Net  on  brake , 95      H.  P. 

Mechanical  efficiency,  per  cent 89 

Back  pressure  work  in  per  cent,  total  work 11.8 

(3  R)s.)        0.213k. 

Expansion 7 

(Boiler  pressure,  56  K>s.  above  atmosphere.) 

Heat  brought  by  dry  steam 0.2604  k.  x  652.48  c.  =  169.90  c. 

"    entrained  water.  .  0.0030  k.  x  152.25  c.  =      0.46  c. 


Total 170.36  c. 

retained  to  condenser. .  .  .0.2634  k.  x  32.25  c.  =      8.49  c. 


Q0  ..............  ...................  161.87  c. 

Heat  gained  by  injection  water  Ql  ..........  8.8131  k.  x  15.72  c.  =  140.38  c. 

Q,—  Qi  ...............  -...  .......................     21.49  c. 

Heat  in  work  done  .......................................  18.77  c. 

"    "    external  radiation  .....  ......  .....................  2.50  c. 

-    21.27  c. 


Heat  per  stroke,  170.36  represents 

Dry  steam  per  stroke  ...................................       rrb  =  °-'2611  k- 

652.48 

"    hour  per  total  H.  P  ..............................  7.822k. 

"      "        "    ind.  H.  P  ...............................  8.837  k. 

11      "        "    net    H.  P..  .  9.929k. 


262  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

II. — Indicated  on  piston 146       H.  P. 

Revolutions  per  minute 30.55 

Net  on  brake 134      H.  P. 

Mechanical  efficiency,  per  cent 92 

Back  pressure  work  in  per  cent,  total  work 9.2 

"«      " (3. libs.)        0.225k. 

Expansion 4 

(Boiler  pressure  52  Ibs.  above  atmosphere.) 

Heat  brought  by  steam 0.3695  k.  x  651.70  c.  =  248.80  c. 

"    entrained..  .  .0.0037  k.  x  149.61  c.  =      0.65  c. 


Total 241.36  c. 

Heat  retained  to  condenser. .  .  .0.3732  k.  x  33.65  c.  =     12.56  c. 


Qn 228.79  c. 

Heat  gained  by  injection  water,  Ql 92917  k  x  21.82  c.  =  202.75  c. 

Qo  —  Qi 26.04  c. 

"    in  work  done 25.27  c. 

"    in  external  radiation 2.50  c. 

27.77  c. 

Error    ^  "^  =  0.7  per  cent. 
Heat  per  stroke,  241.35  c.  represents 

Dry  steam  per  stroke,.  .  . .  ^'^  =  0.3703  k. 

651.70 

"        "      "    hour  per  total  H.  P 8.449  k. 

"      "        "      "    ind.    H.  P 9.307  k. 

•'       "        "      "     net     H.  P 10.341k. 

These  figures  seem  to  prove  that  expansion  has  much  greater  effect 
when  there  is  no  jacket.  Expansion  7  is  7.4  per  .cent,  better  than  4  for  the 
total  and  4  per  cent,  better  for  the  net  H.  P.  Is  this  kept  up  with  super- 
heated steam? 

Superheated  Steam — Him  Engine. 

I.— Indicated  on  piston 113       H.  P. 

Revolutions  per  minute 29.98 

Net  on  brake 102       H.  P. 

Mechanical  efficiency,  per  cent 90 

Back  pressure  work  in  per  cent,  of  total  work 9.7 

(2.6  Ibs.)      0.188  k. 

Expansion 7 

(Boiler  pressure  56  Ibs.  above  atmosphere.) 
Temperature  of  steam  196°  c.  (superheated  44.73°  c.) 

Heat  brought  by  dry  steam 0.2240  k.x  652.48  c.=  146.15  c. 

"          "          "superheating 0.2240  k.x  0.5x44.73  c.=      5.01  c. 

Total. .  . .  151.16  c. 


THE  A LSA  TIA N  EXPERIMENTS,  ETC.  263 


Heat  retained  to  condenser ..  .  .0.2240  k.x 30.42  c.=      6.81  c. 


Q0 144.35  c. 

Heat  gained  by  injection  water,  Q^ 8.7384  k.x  14.05  c.  =  122.77  c. 

Qo-Qi -     21.58  c. 

Heat  in  work  done 19.97  c. 

"    "  external  radiation 2.50  c. 

22.  TC. 

Error     21"58  ~  22'47 =0.6  per  cent. 

lol.lo 

Heat  total  per  stroke,  151.16  c.  represents 
Dry  steam  per  stroke 1^'16  =  0.2317  k. 

Dry  steam  per  hour  per  total  H.  P 6.655  k. 

"ind.  H.P 7.370k. 

"    net    H.P 8.188k. 

II. — Indicated  on  piston 154  H.  P. 

Revolutions  per  minute 30.174 

Net  on  brake 143     H.  P. 

Mechanical  efficiency,  per  cent 93 

Back  pressure  work  in  per  cent,  of  total  work 8.3 

Back  pressure (3  Ibs.)     0.215  k. 

Expansion 4 

Temperature  of  steam  231°c.  (superheated  80.85°c.) 

(Boiler  pressure  55  Ibs.  above  atmosphere.) 

Heat  brought  by  dry  steam 0.3065  k.  x  652.79  c.  =  199.92  c. 

"   superheating 0.3065  k.  x  0.5  x  80.85  c.  =    12.39  c. 

Total , 212.31  c. 

Heat  retained  to  condenser. .  .  .0.3065  k.  x  31.3  c.  =      9.52 c. 


#„  .....................................  ..................  202.72  c. 

Heat  gained  by  injection  water,  &  ...........  9.350  k.  x  18.7  c.  =  174.84  c. 

Q—Q,  .....................................................  27.88  c. 

Heat  in  work  done  ......................................  27.08  c. 

"  in  external  radiation  .................................  2.50  c. 

-  29.58  c. 


Error  —  ^"^"  =  0.8  per  cent. 
/Heat  per  stroke,  212.31  c.,  represents 
Dry  steam  per  stroke..  .................  =  0-32^  k. 

DO  4.  4  £7 

Dry  steam  per  hour  per  total  H.P  ................................  7.000  k. 

"      ind.  H.P  ................................  7.633k. 

"      net    H.P  ................................  8.207k. 

III.  -Indicated  on  piston  ....................................  125  H.  P. 

Revolutions  per  minute  .......................................  30.306 

Net  on  brake  .  ..114H.  P. 


264  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

Mechanical  efficiency,  per  cent 91 

Back  pressure  work  in  per  cent,  total  work 8.9 

(2.7  Ibs.)  0.190  k. 

Expansion 2 

Temperature  of  the  steam  223°  c.  (superheated  73°  c.) 

(Boiler  pressure,  55  Ibs.  above  atmosphere). 

Heat  brought  by  dry  steam 0.2822  k.  x  552.25  c.        =  184.06  c. 

superheating .0.2822  k.  x  0.5  x  73.00  c.  =    10.30  c. 

Total 194.36  c. 

Heat  retained  to  condenser. .  .  .0.2822  k.  x  34.26  c.  =     9.95  c. 


Q0 184.41  c. 

Heat  gained  by  injection  water,  & 8.5983  k.  x  18.76  c.  =  161.20  c. 

<2o-#i 23.11  c. 

Heat  in  work  done 21.86  c. 

"     in  external  radiation 2.50  c. 

•    24.36  c. 

Error  2A"- 206  ercent 

+  94.36 

Heat  total  per  stroke  194.36  c.  represents: 
Dry  steam  per  stroke _ 194'36  =   0.2979  k. 

Dry  steam  per  hour  per  total  H.  P 7.874  k. 

"     "    ind.   H.  P 8.655k. 

"     "    net    H.  P 9.511k. 

The  experiments  with  superheating,  expansion,  4  and  7,  differ  4.9  per 
cent.,  without  superheating  7  per  cent,  of  the  cost  of  a  total  H.  P.  Hold- 
ing account  of  the  superheating  temperature  196°  c.  in  the  first  case,  we 
can  say  that  between  4  and  7  expansions  there  is  7  per  cent,  difference 
with  common  and  superheated  steam.  Introduction  of  J  probably  passes 
below  the  limit  above  which  the  cost  is  nearly  constant. 

The  superheater  arranged  to  work  with  the  normal  conditions,  returns 
less  when  the  consumption  is  reduced,  as  is  the  case  when  expanding  7 
times.  It  can  produce  a  temperature  of  about  220°  c.  when  the  draught 
is  not  influenced  by  atmospheric  conditions.  We  had  a  difference  of  4 
calories,  and  without,  we  should  have  had  a  gain  of  3  per  cent.  more. 

The  experiment  which  best  proves  the  influence  of  expansion  when  it 
passes  certain  limits  is  III.,  cut-off  J,  with  superheating  to  233°,  giving  125 
H.  P.  The  cost  of  a  total  H.  P.  is  15.2  per  cent,  more  than  I.,  and  this  dif- 
erence  would  have  been  greater  if  I.  had  the  same  temperature  of  super- 
heating as  III.,  223°,  instead  of  196°. 

But  we  say  this  experiment  III.  was  made  with  a  throttling  of  1  atmos- 
phere between  beginning  and  end  of  admission. 

We  have  seen  that  throttling  is  far  from  producing  the  effects  and  hav- 
ing the  influence  generally  attributed  to  it.  It  only  brought  the  "Woolf " 
engines,  when  the  normal  load  was  diminished  one-half,  an  increase  of  5 


THE  ALSATIAN  EXPERIMENTS,  ETC.  265 

per  cent,  in  the  cost  of  a  total  H.  P.  Finally,  an  experiment  of  Hirn's, 
verified,  gave,  with  the  same  introduction,  one-half,  and  a  load  reduced 
to  100  H.  P.  gave  the  same  cost  as  with  125,  that  is,  with  20  per  cent,  less 
power. 

Stating,  then,  a  loss  by  throttle  of  only  5  per  cent.,  there  remains  the 
fact  that,  with  two  expansions,  there  is  an  increase  of  10  per  cent,  on  the 
cost  of  a  total  H.  P. 

We  have  rapidly  examined  the  principal  facts  which  stand  in  relief  on 
a  first  approach  to  the  figures  of  consumption.  A  deeper  study  of  the 
phenomena  demands  a  verified  analysis,  which  we  will  give. 

CORLISS  ENGINE — EXPERIMENT  I.,  105  H.  P.;  EXPANSION  11. 

Account  of  heat,  etc.,  per  single  stroke: 

Weight  of  fluid  at  cut-off 0.1370  k. 

"      "    dry  steam  at  cut-off 0.0848  k. 

"      "    water        "        "      38.3  per  cent 0.0522k. 

"      "        "      entrained..  .  0.0043k. 


"      " 


"      condensing  admission  ..........................  0.0479  k. 

Heat  given  to  iron  ........................  0.0479  k.  +  499.77  c.  =    23.93  c. 

Weight  dry  steam  at  end  of  stroke  ...............................  0.1072  k. 

"     water                          "          21.7  per  cent  ..................  0.0298k. 

Internal  heat  at  cut-off,  U0  ......................................  59.55  c. 

"     "    end  of  stroke,  Ul  ..............................  65.87  c. 

U0  —  Z7i  .................................................  6.32  c. 

Heat  furnished  by  jacket  ...................  .  ....................  22.28  c. 

"    iron  above..  23.93  c. 


Heat  furnished  during  expansion 4.66  c. 

"    absorbed  by  total  work  of  expansion 9.57  c. 

"    lost  by  external  radiation 1.5    c. 

Re .- 22.28  —  11.07  =  11.21  c. 

Re,  per  cent,  of  total  heat  ^^  =  12.03  c. 
yu.To 

Check  on  Re. 

Internal  heat  at  end  of  stroke 65.87  c. 

Back  pressure  work 1.21  c. 

Heat  retained  in  condenser 3.17  c. 

"  -     "    cushion..  1.12  c. 


62.79"c. 
Heat  gained  by  injection  water 72.22  c. 

Re 9.43  c. 

Error.  1L219o^89-43  =  1.9  per  cent. 


266  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

CORLISS   ENGINE — EXPERIMENT   II.,    137   H.    P.;   EXPANSION,    8. 

Heat  account,  etc.,  per  single  stroke: 

Weight  of  fluid  present 0.1775  k. 

"  dry  steam  at  cut-off. .  ......  0.1211  k. 


"        "  water  at  cut-off  (31.7  per  cent.) 0.0564  k. 

"      "      entrained 0.0074  k. 

"        "      "      condensed  during  admission 0.0490k. 

Heat  given  to  iron 0.0490  k.  x  499.93  c.  =  24.49  c. 

Weight  of  dry  steam  at  end  of  stroke 0.1434  k. 

"      "    water  at  end  of  stroke  (19.2  per  cent.) 0.0341  k. 

Internal  heat  at  cut-off  U0 82.25  c. 

"     "    end  of  stroke  Z7X : 88.17  c. 

U0~   U, — 5.92c. 

Heat  furnished  by  jacket 5.57  c. 

"  "          "     iron  (above).  .  24.49  c. 


during  expansion 24.14  c. 

"    absorbed  by  total  work  during  expansion 11.50  c. 

"    lost  by  external  radiation 1.50  c. 

Re 24.14  —  13.00  =  11.14  c. 

1114 
Rc  in  per  cent,  of  total  heat  furnished  =  9.8. 

Check  on  Rc: 

Internal  heat  at  end  of  stroke 88.17  c. 

Back  pressure  work 1.38  c. 

Heat  retained  in  condenser —  4.84  c. 

<k          "          "  cushion.,  . .  —1.23  c. 


83.48  c. 
"    gained  by  injection  water 93.18  c. 

Rc 9.70  c. 

Error,11'14-9'70  =  1.2  per  cent. 

-L  i.  t)  •  4:4: 

CORLISS   ENGINE — EXPERIMENT  III,  158   H.  P.;   EXPANSION    6. 

Account  of  heat,  etc.,  per  single  stroke: 

Weight  of  fluid 0.2151  k. 

"        "  dry  steam  at  cut-off 0.1608  k. 

"  water          "        "     (25.3  per  cent.) 0.0543  k. 

"      "    entrained  . .  0.0112  k. 


condensed  at  cut-off. .  0.0431  k, 


THE  ALSATIAN EXPEEIMENTS,  ETC.  267 

Heat  given  to  iron 0.0431  x  498.64  =    21.49  c. 

Weight  of  dry  steam  at  end  of  stroke 0.1753  k. 

"water  "  "  (18.5  per  cent.) 0.0398k. 

Internal  heat  at  cut-off  U0 106.30  c. 

end  of  stroke  U^ .108.13  c. 

ETo—  Z7i — 1-83  c. 

Heat  furnished  by  jacket 5.65  c. 

"    iron   (above) , 21.49  c. 

during  expansion 25.31  c. 

absorbed  by  total  work  of  expansion 12.66  c. 

"    lost  by  external  radiation 1.50  c. 

Re 25.31  —14.16  =    11.15  c. 

Re.  in  per  cent,  of  total  heat  furnished '  a=8. 

139.25 

Check  on  Re. 

Internal  heat  at  end  of  stroke  ETj 108.13  c. 

Back  pressure  work 1.51  c. 

Heat  retained  in  condenser — 6.29  c. 

"  cushion  .  .  .—1.21  c. 


102.07  c. 

"    gained  by  injection  water 111.63  c. 

Re 9.56  c. 

Error,  n-5l-2f6    =1.1  per  cent. 

The  results  of  the  analysis  of  these  three  experiments  upon  the  "Cor- 
liss" engine  at  different  loads  follow  in  order  as  remarkable  as  regular. 
The  increase  of  final  internal  heat  Ult  compared  with  initial  internal  heat 
I70  varies  with  the  water  present  at  cut-off  and  with  the  expansion. 

There  is  an  important  circumstance  which  we  shall  utilize  later  in 
comparing  single  and  double  cylinder  engines.  In  spite  of  the  radical 
difference  in  the  principles  of  construction  of  the  "Corliss"  and  "Woolf" 
engines,  we  see  that  with  13  expansions  for  the  "Woolf"  and  6  for  the 
"Corliss"  the  weight  of  water  at  the  beginning  and  end  of  the  expansion 
and  the  cooling  due  to  the  condenser  are  very  close. 
"Woolf"  engine,  initial  water,  23.7  per  cent.;  final  17.9  per  cent.;  .Rc.8.13 

per  cent.    Expansion  13. 
"Corliss"  engine,  initial  water,  25.3  per  cent.;  final  18.5  per  cent.,  .Re.  8  per 

cent.    Expansion  6. 

With  expansions  28  and  11  there  are  greater  differences. 
"Woolf"  engine,  initial  water,  40  per  cent.;  final  17.6  per  cent.,  Re.  7.8  per 

cent.    Expansion  28. 
"Corliss"  engine,  initial  water,  38.3  per  cent.;  final  21.7  per  cent.,  Re.  1.23 

percent.    Expansion  11. 


268  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


HIRN   ENGINE— EXPERIMENT  I.,  107  H.  P.;  EXPANSION   7. 

Account  of  lieat,  etc.,  per  single  stroke: 

Weight  of  fluid 0.2634  k. 

"        "  dry  steam  at  cut-off. .  .   0.1656  k. 


water  "  37  per  cent 0.0978  k. 

"       entrained..  .  0.0030k. 


"      condensed  at  cut-off 0.0948  k. 

Heat  given  to  iron 0.0948  k.  x  507.35  c.  =    48.10  c. 

Weight  of  dry  steam  at  end  of  stroke 0.1707  k. 

"  water  "          35.2  per  cent 0.0927  k. 

Internal  heat  at  cut-off   U0 114.19  c. 

"          "      "  end  of  stroke  U^ ..  .   109.07  c. 


U0—  Z7, 5.12  c. 

Heat  furnished  from  iron  (above) .  48.10  c. 


during  expansion  ...............................  53.22  c. 

"    absorbed  by  total  work  ........................  .............  13.70  c. 

"    lost  by  external  radiation  .................................  2.50  c. 

Re  ...............................................  53.22  —  16.20  =  37.02  c. 

tyrj  f\n 

Re  in  per  cent,  of  heat  furnished  21.6  c. 

170.36 

Check  on  Re. 

Internal  heat  at  end  of  stroke  C^  ................................  109.07  c. 

Back  pressure  work  ............  ...............................  2.43  c. 

Heat  retained  in  condenser  ..................................  —  8.49  c. 

Re  ...........................................................  37.37  c. 


HIKN  ENGINE—  SATURATED    STEAM,  146  H.  P.,  EXPANSION  4. 

Account  of  heat,  etc.,  per  single  stroke; 
Weight  of  fluid  ..................................................  0.3722  k. 

"  dry  steam  at  cut-off  .................................  0.2571  k. 

"  water  (31  per  cent.)  ..................................  0.1161  k. 

"      entrained.  .  .  0.0037  k. 


"      condensed  at  cut-off 0.1124  k. 

Heat  given  to  iron 0.1124  x  513.76  c.  =    57.73  k. 

Weight  of  dry  steam  at  end  of  stroke 0.2792  k. 

"  water  (25.2  per  cent) 0.0940  k. 

Internal  heat  at  cut-off,  Z70 173.92  c. 

end  of  stroke,  E/i .  175.79  c. 


U9—  U, — 1.87  c. 


THE  ALSA  T1AN  EXPERIMENTS,  ETC.  269 


Heat  furnished  from  iron  (above) 57.73  c. 

during  expansion 55.86  c. 

"    absorbed  by  total  work  of  expansion 15.83  c. 

"    lost  by  external  radiation 2.50  c. 

Re 55.86—  18.33  =  37.53  c. 

Re  in  per  cent,  of  heat  furnished,  -------  =  15.4 

Check  on  Re: 

Internal  heat  at  end  of  stroke,  C7, 175.79  c. 

Back  pressure  work f 2.58  c. 

Heat  retained  after  condensing — 12.56  c. 

165.80  c. 
"    gained  by  injection  water 202.75  c. 

Re 36.95  c. 

Error.  37-53~36-95  =  0.1  per  cent. 

These  two  experiments  offer  a  peculiarity  which  is  worthy  of  atten- 
tion; we  find  equal  weights  of  water  at  the  end  of  the  stroke  0.0927  k.  and 
0.0940  k.  and  the  values  of  Re,  37.02  c.  and  37.53  c.  The  cooling  due  the 
condenser  is,  we  know,  the  heat  carried  by  the  water  on  the  surface  which 
it  covers,  re- evaporating  and  going  to  the  condenser;  the  agreement  with 
the  weight  is  remarkable. 

This  fact  is  not  found  with  the  "Corliss"  engine,  for  Re  is  the  same, 
11.21  c.  and  11.15  c.,  while  the  weights  are  0.0298  and  0.0398  k.  for  expan- 
sion 11  and  6.  We  believe  then  this  is  due  to  the  jacket,  for  the  same 
phenomenon  reversed  is  met  in  the  "Woolf"  engine;  the  weight  of  water 
present  at  the  end  of  the  stroke  of  the  large  piston  is  0.0413  k.  and  0.0431 
k.  nearly  the  same  for  experiments  267  and  185  H.  P.,  while  Re  is  6.65  c. 
and  13.48  c.  respectively. 

HIRN   ENGINE — STEAM   SUPERHEATED   TO    196°   C.;   EXPERIMENT   I.    113   H.  P.; 

EXPANSION  7. 

Account  of  heat,  etc.,  per  single  stroke. 

Weight  of  fluid : 0.2240  k. 

"      "    dry  steam  at  cut-off 0.1688  k. 

"  "  water  "  "  (24.6  per  cent.) 0.0552k. 

Heat  given  to  iron 0.0552  x  506.5  =  27.96  c. 

Weight  of  dry  steam  at  end  of  stroke 0.1761  k. 

"  "  water  "  (21. 38  per  cent) 0.0479k. 

Internal  heat  at  end  of  cut-off,  U0 110.22  c. 

end  of  stroke,  Uj, 108.56  c. 

Z70—  U^. 1.66  c. 


27O  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

Heat  furnished  by  superheating 5.99  c. 

"    iron  (above) 27.96  c. 


during  expansion 35.61  c. 

"    absorbed  by  total  work  of  expansion 14.31  c. 

"    lost  by  external  radiation 2.50  c. 

Re 35.61  —  16.81  =  18.80  c. 

1  ft  ftO 

Re  in  per  cent,  of  total  heat  furnished    -        ~  =  12.5  c. 

151.16 

Check  on  Re: 

Internal  heat  at  end  of  stroke,   C/i 108.56  c. 

Back  pressure  work 2.14  c. 

Heat  retained  after  condensation. .  .  — 6.81  c. 


103.89  c. 
Heat  gained  by  injection  water 122.77  c. 

Re * 18.88  c. 

Error,  18^°:^M§  =  0.05 percent. 
151.16 

HIEN   ENGINE  — STEAM  SUPERHEATED    TO   231°  C.;    EXPEKIMENT   II.,  154  H.  P.; 

EXPANSION  4. 

Account  of  heat,  etc.,  per  single  stroke: 

Weight  of  fluid 0.3065  k. 

"      "  dry  steam  at  cut-off 0.2866  k. 

"  water        "        "     (6.5  per  cent.) 0.0199  k. 

Heat  given  to  iron ' 0.099  X  504.42      10.04  c 

Weight  of  dry  steam  at  end  of  stroke 0.2698  k. 

"      "    water         "        "          "     (12  per  cent.) 0.0367k. 

Internal  heat  at  cut-off,  U0 176.81  c. 

"         "      at  end  of  stroke,  Ul 164.44  c. 

U0—  U, 12.37C. 

Heat  furnished  by  superheating 13.22  c. 

"  iron  (above) ..  10.04  c. 


during  expansion 35.63  c. 

"    absorbed  by  total  work  of  expansion 16.52  c. 

"    lost  by  external  radiation 2.50  c. 

Re 35.63  —  19.02  =  16.61  c. 

Re  in  per  cent  of  heat  furnished  ^~  =  7.8    c. 

212.31 

Check  on  Re: 

Internal  heat  at  end  of  stroke,  l/i 164.44  c. 

Back  pressure  work 2.45  c. 


THE  ALSATIAN  EXPERIMENTS,  ETC.  271 

Heat  retained  after  condensing  ................................        9.59  c. 

157.30  c. 
"    gained  by  injection  water  .................................     174.84  c. 

Re  ..........................................................       17.54  c. 

Error  -7:5^  0.4  per  cent. 


HIBN    ENGINE—  STEAM    SUPERHEATED    TO  223°   C.;   EXPERIMENT   III.,    125 
H.  P.;   EXPANSION  2. 

Account  of  heat,  etc.,  per  single  stroke. 
Weight  of  fluid  .................................................     0.2822  k. 

Weight  of  dry  steam  at  cut-off  ..................................     0.2866  k. 


"        water  at  cut-off  (superheated)  .......................  —  0.0044  k. 

"        dry  steam  at  end  of  stroke  ...........................     0.2449  k. 

"        water  at  end  of  stroke  (13.2  per  cent.)  ...............    0.0373  k. 

Internal  heat  at  cut-off,   U0  ......................................     169.93  c. 

end  of  stroke,  U,  ................................     149.42  c. 


U0—  £/!  ......................................................  20.52  c. 

Heat  furnished  by  superheating  ................................  11.56  c. 

during  expansion  .................  .....'  .........  32.68  c. 

"     absorbed  by  total  work  of  expansion  ......................  9.24  c. 

"     lost  by  external  radiation  .............  .  ..................  2.50  c. 

Re  ........................................  .  .......  32.08  —  11.74  =  20.34  c. 

OQ     OJ_ 

Re  in  per  cent,  of  heat  furnished  —    -  =  10.5  c. 

194.  36 

Check  on  Re 

Internal  heat  at  end  of  stroke  ...............................  ____  149.42  c. 

Back  pressure  work  .............................................  2.17  c. 

Heat  retained  after  condensing  ..................................  —  9.49  c. 

141.64  c. 

"     gained  by  injection  water  .......  .........................  161.30  c. 


Re  ...........................................................  ...       19.66  c. 


The  three  values  of  Re,  18.80  c.,  16.61  c.  and  20.34  c.,  vary  little;  we  can 
therefore  state  that  these  figures  do  not  agree  with  the  weight  of  water  at 
the  end  of  the  stroke.  Thus  for  experiments  II.  and  III.  the.  final  weights 
of  water  are  0.0367  k.  and  0.0373  k.,  very  near  each  other,  while  Re  is  16.61 
c.  and  20.34  c.  We  recognize  here  the  effect  of  superheating,  for  under 
the  same  conditions  saturated  steam  gave  equal  weights  of  water  and 
equal  values  of  Re.  It  is  to  be  remarked  that  the  highest  cooling  by  the 


272  STEAM  USING;  OH,  STEAM  ENGINE  PRACTICE. 


condenser  corresponds  to  the  lowest  work  and  the  longest  admission  ^ 
superheated. 

With  jacket,  on  the  contrary,  the  largest  value  of  Re  is  with  the  long- 
est expansion,  11,  of  the  "Corliss,"  or  to  the  least  work,  185  H.  P.,  of  the 
"Wool!"  engine.  The  reason  is  that  the  jacket  gives  up  heat  during 
exhaust  proportionally  to  the  difference  of  temperature,  while  with  super- 
heating and  saturated  steam  the  heat  is  stored  in  the  surface.  Also  we  see 
that  the  difference  16  to  20  c.  is  much  less  than  for  the  "Woolf "  engine,  6 
to  13  c.,  while  for  equal  values  of  Re,  11  c.,  we  have  in  the  "Corliss"  0.0298 
and  0.0398  k.,  varying  3  to  4,  while  with  superheating  the  values  of  Re 
vary  4  to  5. 

Finally,  we  see  the  proportion  of  steam  condensed  during  admission 
diminish  rapidly,  with  the  expansion  passing  from  24.6  to  6.5  to  0  in  exper- 
iments I.,  II.  and  III.,  while  in  this  last  case  we  find,  if  we  calculate  by 
volume  and  weight  the  steam  at  cut-off,  we  get  more  than  that  given  by  the 
direct  measurement.  The  steam  occupying  the  volume  at  cut-off  possesses 
an  excess  of  heat,  which  is  betrayed  by  the  greater  pressure  than  would 
be  given  by  the  same  weight  of  saturated  steam  occupying  the  same  space. 

It  is  then  incorrect  to  say  that  superheated  steam  falls  to  the  condition 
of  saturated  steam  always,  and  partially  condenses  on  arriving  in  the 
cylinder;  it  is  also  wrong  to  attribute  to  the  initial  condensation  all  the 
loss  of  pressure  observed  between  the  boilers  and  cylinders.  These  losses 
of  pressure  are  mainly  due  to  restrictions  in  the  pipes  and  passages;  this 
is  proved  by  this  experiment  where  the  steam  at  cut-off  is  superheated  and 
where  the  condensation  cannot  be  the  cause  of  such  loss  of  pressure. 

Influences  of  various  expansions  upon  single  cylinder  engines— their  utility 
from  the  point  of  view  of  cost. 

Uniting  in  a  single  table  (on  opposite  page)  the  results  of  our  analyses 
we  shall  render  the  discussion  easier. 

The  general  effect  of  a  prolonged  expansion  appears  the  same  whether 
it  be  a  question  of  one  cylinder  or  two;  whether  jacketed  or  not.  It  is 
to  be  remarked  that  the  phenomenon  is  much  more  regular  when  the 
expansion  is  produced  in  the  same  inclosure,  the  order  of  transfers  of  heat 
is  continuous,  while  the  large  cylinder  of  the  "Woolf"  engines  gives  birth 
to  singular  modifications  in  the  thermic  action  of  the  surfaces.  This 
peculiarity  we  have  had  occasion  to  note  for  the  experiment  with  expan- 
sion 13,  and  introduction  of  one- half  the  small  cylinder. 

The  increase  of  expansion  always  causes  an  increase  in  the  proportion 
of  steam  condensed  during  admission,  and  a  decrease  in  the  amount  of 
dry  steam  per  total  H.  P.  per  hour;  but  this  double  action  is  more  or  less 
energetic  as  the  engine  is  provided  with  a  jacket  or  not,  and  according  as 
saturated  or  superheated  steam  is  used,  which  the  figures  of  Table  IV  will 
prove  to  us. 

Notwithstanding  the  reputation  of  the  "Corliss"  and  its  derivatives 
we  have  studied  them  as  a  single  cylinder  jacketed,  with  four,  valves. 


TBS  ALSATIAN  EXPERIMENTS,  ETC. 


273 


TABLE  IV. 


HIBN  WITHOUT  JACKET. 


COBLISS,  WITH  JACKET. 

Saturated. 

Superheated. 

No.  of  expansions  
Force  indicated  on  pis- 
tons, H.  P 

I. 

11 
105 
7.188 
10 
7.983 
88 
9.071 
3 
6.5 
38.3 
21.7 
—6.32 
11.21 
12.03 

II. 

8 
137 
7.236 
8.8 
7.939 
91 
8.724 
4 
6 
31.7 
19.2 
—5.92 
11.14 
9.8 

III. 

6 
158 
7.307 
8.1 
7.955 
92 
8.646 
5.2 
5.3 
25.3 
18.5 
-1.83 
11.15 
8 

I. 

7 
107 
7.822 
11.8 
8.837 
89 
9.929 
1.1 

37 
35.2 
+5.12 
37.92 
21.6 

n. 

4 

146 
8.449 
9.2 
9.307 
92 
10.341 
1.0 

31 
25.2 

—1.87 
37.53 
15.4 

I. 

196° 

7 

113 
6.655 
9.7 
7.370 
90 
8.188 

24.6 
21.4 
+1.66 
18.80 
12.5 

n. 

231° 
4 

154 
7.000 
8.3 
7.633 
93 
8.287 

6.5 
12 
+  12.37 
16.61 

7.8 

in. 

223° 
2 

125 
7.874 
8.9' 
8.655 
91 
9.511 

* 
13.2 
+20.52 
20.34 
10.5 

Dry  steam  per  hour  per 
total  H.  P.,  ks  

Back  pressure  work  per 
cent,  of  total  work.  .  . 
Dry  steam  per  hour  per 
Ind.  H.  P.,ks  

Mechanical  efficiency, 
per  cent  

Dry  steam  per  hour  per 
net  H.  P.,  ks  ... 

Per  cent,  water  carried 
over 

Per  cent,  water  con- 
densed in  jacket  

Per  cent,  water  contain- 
ed at  cut-off  

Percent,  water  contain- 
ed at  end  of  stroke.  .  . 
Uo  —  Ui  during  expan- 
sion, cs    .  . 

Re  loss  by  cooling  due 
condenser,  cs  . 

Re  in  per  cent,  of  total 
heat  furnished 

Without  doubt  the  arrangement  with  circular  valves  and  the  releasing  gear 
are  very  ingenious  and  offer  a  certain  interest,  but  practically  we  much 
prefer  fiat  valves  with  right  line  movements  moved  by  cams  or  eccentrics; 
they  always  close  tight  in  consequence  of  the  very  nature  of  their  work- 
ing. We  have  seen  "Woolf"  engines  with  the  valve  seat  in  perfect  order 
after  twenty  years'  working.  The  Hirn  engine  with  four  slide  valves, 
with  seats  smooth  and  close  to  the  cylinder,  presents  no  defects  after 
twenty-five  years.  This  reservation  made,  we  will  pass  to  the  examina- 
tion of  the  three  cases  of  the  single -cylinder  jacketed  engine  with  four 
valves. 

The  expansion  changing  from  6  to  14,  the  proportion  of  initially  con- 
densed water  increases  from  25  to  38  per  cent.,  a  change  of  13  per  cent. 
At  the  end  of  the  stroke  the  difference  is  less  marked,  from  18  per  cent,  to 
21  per  cent.  This  proves  a  greater  evaporation  for  the  greater  expansion. 
The  heat  required  is  drawn  from  the  jacket  and  surface  which  has  re- 
ceived it  during  the  admission.  But  I  do  not  insist  upon  this  series  of 
phenomena  discovered  by  M.  Hirn  and  described  by  him,  for  I  have 
treated  them  at  sufficient  length  in  an  elementary  form  in  my  paper  of 

*Superheated. 


274  STEAM  USING;  OB,  STEAM  ENGINE  PRACTICE. 

25th  October,  1876  (Bulletins  for  March,  April,  May,  1877),  concerning  the 
experiments  executed  under  his  direction. 

That  which  we  should  remark,  however,  is  that  this  progress  crosses 
the  difference  Z70— C/i  between  the  internal  initial  and  final  heats,  the  lat- 
ter becoming  greater  as  the  expansion  is  increased.  The  "  Woolf "  engines 
with  variable  expansion  and  jacket  have  already  presented  the  same  phe- 
nomenon. Is  it  then  one  of  the  effects  of  the  expansion?  or  is  it 
an  effect  of  the  jacket?  The  study  of  the  Hirn  engine  permits  us  to 
decide. 

We  have  seen  that  the  proportion  of  water  at  the  end  of  the  stroke 
for  the  "Corliss"  differs  3  per  cent.,  while  the  weight  of  water  is  0.0298  k. 
for  11  expansions,  0.0341  k.  for  9,  and  0.0398  for  6;  the  value  Re  is  also  a 
function  of  this  weight  of  water,  since  the  loss  Re  is  the  amount  of  heat 
required  to  evaporate  a  portion  of  water  on  the  surface  and  return  it  to 
the  condenser  in  the  shape  of  steam.  How  is  it  then  that  the  three  values 
of  .Re  are  equal  to  11  calories,  when  the  weights  are  as  1,  0.85,  0.75?  The 
same  phenomenon  presents  itself  with  the  "Woolf"  engines,  but  in  a  man- 
ner reversed:  in  that  we  have  different  coolings  with  the  same  weights  at 
the  end  of  the  stroke.  Thus  for  B  and  F,  expansion  6  and  25,  the  weights 
are  0.0706  and  0.0685  k.  of  contained  water,  while  the  values  of  Re  are 
8.44  c.  and  21.33  c.  Is  this  still  the  effect  of  expansion?  But  then  in  the 
same  expansion  equal  weights  of  water  should  give  equal  values  of  Re., 
and  we  should  not  have  with  the  Munster  engine,  expanding  7  times, 
values  of  Re,  6.65  c.  and  13.48  c.,  when  the  weight  of  terminal  water  is 
0.0413  k.  and  0.0430  k.  for  267  and  185  H.  P.  Still,  a  question  to  which  the 
experiments  on  the  Hirn  engine  will  give  a  solution. 

The  intrinsic  values  of  the  different  expansions  are  fixed  as  we  have 
said  by  the  cost  of  a  total  H.  P.  The  economy  realized  by  the  work  of 
steam  is  2.15  per  cent,  between  expansion  6  and  11  for  the  "Corliss"  en- 
gine ;  but  this  benefit  does  not  exist  industrially,  the  most  economic 
being  expansions  4.6  per  cent,  better  than  11.  We  can  state  here  again, 
for  single -cylinder  engines,  the  fact  that  our  analyses  established  for 
"Woolf"  engines  jacketed  that  prolonged  expansions  are  far  from  being 
economical  in  practice. 

The  Hirn  engine,  without  jacket,  consuming  saturated  steam  with  ex- 
pansions of  4  and  7,  offers  initial  condensations  of  31  and  37  per  cent. ;  with 
the  latter  the  terminal  value  is  nearly  the  same,  35  per  cent.,  while  the 
former  has  evaporated  6  per  cent.,  which  is  the  reverse  of  jacketed  en- 
gines. In  these,  a  large  expansion  gives  a  larger  evaporation  ;  the  super- 
heating also  gives  a  large  evaporation  with  a  less  condensation  for  the  ex- 
pansions which  augment  it.  With  expansions  of  2,  4  and  7,  the  steam  re- 
mains superheated  for  the  first,  and  for  the  two  others  condenses  at  the 
end  of  admission,  6  and  24  per  cent,  at  the  end  of  the  stroke.  The  propor- 
tions of  contained  water  are  13,  12  and  21  per  cent.  For  the  first  case  the 
superheated  steam  becomes  saturated  and  then  condenses  13  per  cent, 
during  the  expansion,  for  the  second  the  proportion  of  water  increases  6, 
and  for  the  last  only  3  per  cent,  to  the  end  of  the  stroke. 


THE  AL8A  TIAN  EXPERIMENTS,  ETC.  275 

With  regard  to  the  surface  condensation  and  evaporation,  the  super- 
heating acts  partly  as  a  jacket.  Its  influence  upon  the  internal  heat  Z7T 
and  cooling  due  the  condenser  Re  should  present  the  same  analogies,  for 
these  quantities  of  heat  are  in  intimate  relation  with  the  weights  of  water 
present  at  the  commencement  and  end  of  the  expansion  ;  but  the  study  of 
U  and  Re  will  show  us  that  the  action  of  superheating  is  less  energetic 
upon  them  than  a  jacket,  but  that  it  conducts  to  an  economy  at  least 
equal  if  not  greater  upon  the  consumption  of  steam. 

If  we  work  the  Hirn  engine  with  saturated  steam,  the  internal  heat  U^ 
grows  less  with  regard  to  U0  when  the  expansion  is  increased.  The  dif- 
ference Z7i  —  U0  =  —  1.87  c.  with  4,  and  becomes  5.12  c.  for  7  expansions. 
The  jacketed  engines  gave  a  reversed  difference;  the  final  internal  heat  is 
there  increased  with  regard  to  the  initial,  when  the  expansion  was  pro- 
longed. The  jacket  is  then  the  only  cause  of  this  accession  of  internal 
final  heat  following  the  order  of  expansion.  This  is  also  the  manner  of 
action  with  superheating,  for  we  see  the  difference  Ul—  U0  pass  from  20.52 
c.  to  12.37  c.,  and  to  1.66  c.  when  the  expansions  are  2,  4  and  7. 

The  remarkable  action  of  the  jacket  upon  different  expansions,  and 
the  analogous  but  less  strongly  marked  effect  of  superheating,  are  more 
especially  characterized  by  the  successive  values  which  the  cooling  due 
the  condenser  Re  acquires.  The  Hirn  engine  without  superheating,  with 
expansions  4  and  7,  presents  the  same  weight  of  water,  0.0940  k.,  and  0.0927 
k.  at  the  end  of  the  stroke,  the  values  of  Re  are  37.53  c.  and  37.02  c.  Note 
well  that  it  is  not  necessarily  thus,  that  the  thermic  conditions  of  the  sur- 
faces could  and  should  differ  with  expansions  4  and  7.  This  remarkable 
fact  proves  to  us  that  without  a  jacket  and  with  saturated  steam  the  weight 
of  final  water  decides  the  value  of  Re.  If,  however,  we  give  to  the  steam 
an  excess  of  heat  and  superheat  it,  we  see  that  with  equal  weights  of  water 
at  the  end  of  the  stroke,  0.0373  k.  and  0.0367  k.  with  expansions  2  and  4, 
we  have  values  of  jRc,  20.34  c.  and  16.61  c.,  differing  3.7  c.,  when  with 
saturated  steam  they  were  equal;  but  it  is  with  jacketed  engines  that  the 
difference  is  greatest.  Experiments  B  and  F  on  the  Malmerspach  engine, 
expansions  6  and  25,  have,  as  we  have  seen,  values  of  Re,  8.44c.  and  21.33  c. 
for  weights  0.0706  k .  and  0.0682  k.  The  Munster  engine  offers  Re,  6.65  c. 
and  13.48  c.  for  267  and  185  H.  P.,  the  weight  of  water  being  0.0413  k.  and 
0.0431  k.  Finally,  the  "Corliss,"  with  .Re  =  11  c.  for  expansions  6  and  11, 
has  terminal  water  0.0398  k.  and  0.0298  k. 

There  is  a  particular  mode  of  working,  which,  singular  and  energetic 
as  it  seems,  should  find  its  natural  explanation  when  carefully  studied. 
The  cooling  by  the  condenser  Re  is,  as  we  have  many  times  said,  the 
heat  drawn  from  the  surface  by  the  evaporation  of  a  part  of  the  water 
which  covers  it,  and  the  passage  to  the  condenser  of  the  water  as  steam. 
This  heat  furnished  by  the  iron  surface  is  given  in  two  ways,  according  as 
the  engine  is  jacketed  or  not.  If  saturated  steam  arrives  in  a  cylinder 
without  this  improvement,  it  partially  condenses  during  admission,  giving 
up  thereby  a  certain  quantity  of  heat  to  the  metal,  which  restores  it  during 
expansion  and  exhaust.  We  have  stated  that  in  this  case  and  in  the  limits  in 


276  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

which  we  have  operated,  the  values  of  Re  are  equal  for  equal  weights  of  ter- 
minal water.  Substituting  superheated  steam  for  saturated  steam,  the  heat 
furnished  the  iron  surface  during  admission  will  be  differently  restored 
during  the  exhaust.  Equal  weights  of  terminal  water  give  different  values 
of  Re,  a  loss  of  3.7  c.  more  corresponding  to  the  greater  expansion.  But  it 
is  with  the  jacket  that  the  loss  Re  increases  with  the  expansion  for  equal 
weights  of  terminal  water;  here  the  heat  is  notonly  stored  in  the  metal  sur- 
face during  admission,  it  is  furnished  from  without  across  the  thickness  of 
metal  by  steam  from  the  boiler  condensing  on  the  cylinder.  This  conden- 
sation is  greatest  when  the  difference  of  temperature  is  greatest  between  the 
steam  in  the  cylinder  and  the  jacket,  that  is  to  say,  during  exhaust.  This 
transfer  of  heat  accelerates  the  evaporation  of  the  water  which  lines  the 
interior  surface,  augmenting  the  value  of  the  loss  Re.  Such  is  the  cause 
which  in  most  cases  renders  the  jacket  less  effective  than  superheating 
moderately;  that  its  action  appears  at  first  sight  more  energetic  we  should 
remember  that  it  makes  the  difference  of  heat  that  it  gives  the  expansion 
and  the  waste  heat  that  it  gives  the  condenser  a  larger  quantity  than  is 
given  by  superheating. 

The  influence  of  a  greater  or  less  expansion  appears  to  be  more  with 
un jacketed  engines,  at  least  this  is  the  case  with  the  Him  engine  between 
4  and  7  expansions.  With  saturated  steam  the  costs  of  a  total  H.  P.  are 
8.449  and  7.822  k.  which  differ  7.4  per  cent.  The  same  costs  with  super- 
heated steam  are  7.000  and  6.665k.;  at  the  same  expansions  they  differ 
4.9  per  cent.,  being  less  than  for  saturated  steam.  But  we  should  hold 
account  also  that  the  steam  has  not  been  obtained  at  the  same  tempera  - 
ture  in  these  two  experiments.  If  the  superheating  had  been  the  same, 
the  difference  would  have  been  2  per  cent,  more,  or  7  per  cent.,  whether 
the  engine  works  with  or  without  superheating.  Is  it  then  only  an  effect 
of  the  absence  of  a  jacket,  or  should  we  consider  it  as  caused  by  an  intro- 
duction already  too  great  in  the  cylinder?  We  are  brought  to  believe 
that  these  causes  both  act,  for  with  superheating  and  introduction  of  one- 
half  there  is  a  difference  of  15.2  per  cent,  more  than  in  the  experiment 
with  7  expansions,  a  difference  which  would  have  been  still  greater  if  the 
temperature  of  the  steam  in  this  last  experiment  had  been  223°  C.  instead 
of  196°  C. 

We  see  from  the  cost  of  a  total  H.  P.  which  fixes  the  value  of  the  in- 
trinsic work  of  steam,  and  to  which  we  could  give  the  name  of  generic 
cost,  offers  a  marked  advantage  for  the  prolonged  expansion  7,  as  well  for 
saturated  and  superheated  steam.  This  advantage  diminishes  in  practice, 
the  back  pressure  and  friction  not  varying  with  the  useful  work.  That  is 
with  superheated  steam  the  cost  of  a  net  H.  P.  is  the  same  8.188  k.  and 
8.207  k.,  when  the  generic  costs  differ  4.9  per  cent,  for  expansions  7  and  4 
with  saturated  steam,  and  the  same  expansions  the  generic  economy  7.4 
per  cent,  becomes  a  practical  economy  of  4  per  cent.  We  found  with  the 
"Corliss"  that  the  generic  economy  of  2.15  became  a  practical  loss  of  4.6 
when  the  expansion  changed  from  6  to  11. 

These  results  bring  us  to  the  conclusion  we  have  already  stated 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  277 


for  "Woolf"  engines  jacketed,  they  confirm  experimentally  the  theoretic 
advantage  of  large  expansions  established  by  M.  Zeuner;  at  the  same 
time  the  practical  advantage  of  moderate  expansions,  preconceived  by  M. 
dim. 


COMPARISON  OF  EXPERIMENTAL  VALUES  FOR  DOUBLE  AND  SINGLE  CYLINDER 
ENGINES — CONCLUSIONS. 

Before  stating  the  figures  which  serve  for  this  study  let  us  recall  some 
principles  which  it  is  indispensable  to  keep  well  in  mind  during  the 
course  of  the  discussion. 

We  have  determined  for  each  experiment  the  number  of  calories 
brought  to  the  cylinder  per  stroke,  as  well  as  the  consumption  of  dry 
saturated  steam  that  it  represented.  This  calculation  had  for  its  object 
to  bring  all  the  engines  to  the  same  unit  of  comparison.  Thus  all  the  en- 
gines which  we  have  examined,  whether  jacketed  or  not,  whether  using 
superheated  steam  or  not,  consume  a  certain  number  of  calories  per  stroke, 
which  can  be  represented  by  a  weight  of  dry  steam  produced  by  the 
boiler  at  the  pressure  of  the  experiment.  By  operating  in  this  manner 
we  preserve  a  rigorously  exact  unit,  while  approaching  the  old  valuation 
which  established  the  consumption  of  steam  taken  by  the  cylinder  with 
more  or  less  water  and  even  superheated. 

It  is  not  necessary  to  say  that  this  weight  of  dry  steam  is  not  that 
which  we  study  in  the  cylinder;  in  all  the  analyses  we  naturally  hold  ac- 
count of  the  weight  really  existing  in  the  engine. 

This  consumption  of  dry  steam  is  then  presented  in  three  forms,  em- 
bracing each  a  particular  order  of  facts.  The  cost  per  hour  of  a  total  H. 
P.,  of  an  indicated  H.  P.,  and  of  a  net  H.  P. 

The  first  supposes  a  perfect  vacuum,  and  we  get  rid  of  the  construction 
of  the  engine,  and  sometimes  of  the  system  adopted;  in  a  word,  we  have 
the  intrinsic  value  of  the  work  of  the  steam.  In  comparing  them,  we  are 
in  a  manner  studying  the  use  of  the  heat — of  the  heat  brought  to  the 
engine. 

The  second  holds  account  of  the  back  pressure  work,  which  varies 
from  one  experiment  to  the  other  upon  the  same  engine  with  different 
loads.  It  is  the  cost  referred  to  the  measure  of  the  area  of  the  indicator 
diagrams. 

Finally  the  cost  of  a  net  H.  P.  takes  into  account  the  friction  of  the 
engine  and  is  the  industrial  value,  more  or  less  economic,  of  the  engine  ; 
it  corresponds  to  the  force  measured  by  the  brake. 

To  each  of  these  three  kinds  of  consumption  corresponds  a  method 
of  working  characteristic  of  engines  with  one  or  two  cylinders.  This 
mode  of  working  we  will  define,  and  join  therewith  the  different  results 
which  indicate  the  kind  and  value  of  the  transfers  of  heat. 

In  the  series  of  our  eighteen  experiments  we  find  two  experi- 
ments of  which  the  figures  are  closely  alike  ;  they  can  only  be  distinguished 


278  STEAM  USING;  OK,  STEAM  ENGINE  PRACTICE. 

by  the  cost,  and  are  eminently  suited  for  an  exact  comparison  of  single 
and  double  cylinder  engines. 

These  are  the  experiments  upon  the  "  Woolf,"  expanding  13,  and  the 
"Corliss,"  expanding  6.  The  proportions  of  contained  water  differ  little, 
25.3  for  the  beginning  and  18.5  for  end,  for  the  "Corliss  "  ;  23.7  and  17.9  per 
cent,  for  the  "  Woolf." 

The  internal  initial  and  final  heats  are  nearly  constant,  106.30  c.-~ 
108.13  c.  =  —  1.83  c.  =  U0  —  Ux  and  283.55  c.  —  282.31  c.  =  1.24  c.  The 
"  Woolf  "  presents  a  peculiarity  which  we  have  already  noticed.  Dur- 
ing the  expansion  in  the  "  Corliss  "  engine  a  continuous  evaporation  of 
6.8  per  cent,  took  place.  In  the  "  Woolf  "  engine  the  phenomenon  is  not 
so  simple.  We  have  in  the  total  expansion  an  evaporation  of  5.8  per  cent.; 
but,  because  of  the  arrangement  with  two  cylinders  and  the  introduction 
to  half  stroke  in  the  small  cylinder,  the  expansion  is  broken  into  two  por- 
tions, in  each  of  which  the  transfers  of  heat  in  a  manner  differ. 

The  expansion  in  the  small  cylinder  during  the  last  half  of  the  stroke 
gives  rise  to  an  evaporation  of  10.3  per  cent,  of  the  water  inclosed  with 
the  steam,  the  internal  heat  is  augmented  TJ0  —  Ul  =  283.55  c.  —  305.84  c.  = 
—  22.29  c.,  much  more  rapidly  than  in  the  corresponding  experiment  with 
the  "Corliss,"  and  is  with  13.1  water.  When  the  mixture  passes  to  the  large 
cylinder  at  the  end  of  the  stroke,  the  weight  of  the  water  is  17.9  per  cent., 
there  has  been  4.8  per  cent,  of  the  fluid  condensed  in  the  second  part  of 
the  expansion. 

The  modification  of  the  thermic  phenomena  by  an  expansion  com- 
menced at  half  the  small  cylinder  is  radical,  as  we  see  ;  it  seems  to  prove 
the  inaction  of  the  jacket.  We  haTTe  seen  that  the  jacket  counteracts  in 
part  the  energetic  condensations  which  are  produced  at  the  commence- 
ment of  the  stroke  of  the  large  piston. 

The  fact  which  we  note,  joined  to  the  values  of  the  cooling,  by  the 
condenser,  for  the  two  experiments  should  reduce  to  their  just  value  the 
edifying  considerations,  outside  of  experimental  grounds,  which  show 
the  superiority  of  "  Woolf  "  engines. 

The  too  widely  diffused  opinion  still  is  that  for  stationary  as  for  mar- 
ine engines  the  double- cylinder  jacketed  engine  is  actually  that  which 
gives  the  best  economic  return  in  the  production  of  motive  power. 

"  In  these  engines  the  steam  acts  first  with  or  without  expansion  in  the 
small  cylinder,  then  with  expansion  in  the  large  cylinder.  This  latter  is 
then  alone  in  communication  with  the  condenser.  By  this  disposition  a 
portion  of  the  force  produced  escapes  the  cooling  action  of  the  condenser 
and  the  cylinder  condensation. 

"  Further,  because  of  the  jackets  in  which  the  two  cylinders  are  placed 
in  the  midst  of  steam  from  the  boiler  direct,  the  expanding  steam  in  the 
large  cylinder  is  at  a  much  lower  temperature  than  that  of  the  jacket,  and 
consequently  is  easily  warmed  and  the  cylinder  condensation  notably 
lessened." 

These  deductions,  which  appear  so  logical  that  I  myself  believed  them 
rational  enough  (1874-75),  receive  the  formal  condemnation  of  experience, 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  279 

This  proves  once  more  that  it  is  impossible,  as  M.  Hirn  has  said,  to  estab- 
lish a  priori  anything  that  shall  be  tolerably  exact  concerning  steam  en- 
gines. "A  correct  theory  can  only  be  established  a  posteriori,  that  is  to  say, 
after  the  experimental  study  of  each  special  system  of  engines."  We  shall 
see  at  the  same  time  that  it  is  important  to  collect  together  the  discover- 
ies that  M.  Hirn  calls  by  the  name  of  the  "practical  theory  of  the  steam 
engine."  This  theory  will  enable  us  to  establish  on  a  certain  basis  and 
with  the  most  minute  details  the  comparative  experimental  values  of 
the  different  systems  of  steam  engines. 

It  is  generally  admitted,  we  will  say,  that  the  arrangement  with  two 
cylinders  ought  to  withdraw  a  portion  of  the  force  produced  from  the 
cooling  action  of  the  condenser;  how  is  it  then  that  we  have  Re  8  and  8.3 
per  cent,  for  the  "  Woolf  "  and  the  "  Corliss  "  ?  This  same  arrangement, 
where  the  expansion  is  made  in  the  large  .cylinder  with  a  steam  jacket 
which  warms  it  easily,  should  diminish  the  condensation.  Whence  comes 
then  the  condensation  of  5  per  cent.,  which  we  have  found,  when,  on  the 
contrary,  the  "Corliss"  and  the  small  cylinder  present  evaporations  of  7 
and  10  per  cent,  during  the  expansion.  Two  hypotheses  which  appeared 
to  have  a  certain  basis  are  annulled  by  the  analysis;  they  should  put  us 
on  our  own  guard  against  all  researches  which  are  not  purely  experimen- 
tal and  verified. 

The  two  experiments  which  we  compare  have  the  same  proportion  of 
initial  and  final  water,  25  and  18  per  cent.,  the  same  loss  by  the  condenser, 
8  per  cent.,  for  both  the  internal,  initial  and  final  heat  are  nearly  con- 
stant. 

The  consumption  of  dry  steam  should  then  fix  for  us  the  relative 
value  of  single  and  double  cylinder  engines  with  jackets,  but  they  should 
not  be  admitted  without  preliminary  discussion. 

The  consumption  of  dry  steam  per  total  H.  P.  gives,  as  we  have  said, 
the  intrinsic  value  of  the  work  of  the  steam;  it  is  6.878  k.  for  the  "  Woolf," 
expanding  13,  and  7.307  k.  for  the  "Corliss,"  expanding  6,  being  5.9  per 
cent,  in  favor  of  the  "  Woolf."  This  figure  fixes  at  6  per  cent.,  the  intrin- 
sic economy  realized  by  expansion  in  a  separate  cylinder;  if  it  was  not 
submitted  to  two  important  corrections  in  passing  from  the  domain  of 
theory  to  the  realm  of  industrial  practice,  it  would  seem  to  give  reason  to 
the  partisans  of  this  system. 

But  before  making  these  two  corrections,  we  should  notice  that  these 
two  experiments  have  been  made,  with  all  their  similar  features,  with 
different  expansions.  An  expansion  of  13  gave  with  the  "Corliss"  an  econ- 
omy of  1.5  per  cent.,  and  we  can  affirm  without  committing  sensible  error, 
that  an  expansion  of  13  would  give  2  per  cent,  improvement,  which  re- 
duces to  4=  per  cent,  the  generic  economy  of  expansion  in  the  large  cylin- 
der. It  is  not  large,' as  we  see,  and  this  disappears  completely,  giving 
place  to  a  considerable  increase  in  practice. 

In  a  note  presented  to  our  society  (session  Aug.  26,  1874)  and  appear- 
ing in  the  Bulletin  in  1875  I  studied  the  variations  of  back  pressures  in 
steam  cylinders,  with  the  values  of  negative  work  in  terms  of  total  work. 


28O  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

This  study  proved  that  the  negative  work  absorbed  15  per  cent,  of  the 
total  work  in  "Woolf "  engines,  and  7  per  cent,  only  in  "Corliss"  engines, 
the  back  pressure  work  being  the  same— 0.210  to  0.217  in  the  two  cases  (2.9 
and  3.0  tbs.).  These  results  were  established  where  the  proportions  of 
total  work  absorbed  by  the  back  pressure  remained  constant.  The  two 
experiments  which  occupy  us  have  not  the  same  vacuum,  that  of  the  "Cor- 
liss" is  a  little  better  than  the  "Woolf,"  0.184  to  0.226  k.,  making  8  per  cent, 
instead  of  7  per  cent,  for  we  are  within  the  stated  limits;  with  a  back  pres- 
sure of  0.226  k.,  the  negative  work  of  the  "Corliss"  would  have  been  9  per 
cent.  It  is  thus  proved  that  with  the  same  vacuum  of  0.226  k.  by  the  fact 
of  adding  a  second  cylinder  to  prolong  the  expansion  we  create  a  serious 
loss;  this  loss  destroys  the  genuine  economy  that  we  have  established  for 
double-cylinder  engines  from  the  consumption  per  total  H.  P. 

We  shall  not  be  astonished  then  that  the  "Corliss"  leads  2.3  per  cent.. 
Avhen  we  compare  the  cost  per  indicated  H.  P.,  over  the  "Woolf." 

Finally,  the  last  brake  experiments  by  our  Mechanical  Committee  have 
proved  that  there  is  a  notable  difference  in  the  power  absorbed  in  friction 
of  the  moving  parts  in  two  horizontal  engines,  of  which  one  had  a  single 
cylinder  while  the  other  had  two  cylinders,  "Woolf"  system.  This  infe- 
riority adds  its  influence  to  the  negative  work  and  brings  the  two  follow- 
ing consumptions  pernet  H.  P.;  "Corliss," 6  expansions,  8.646  k.;  "Woolf," 
13  expansions,  9.465  k.  Such  are  the  weights  of  dry  steam  valued  on 
a  Prony  brake;  they  represent  the  quantities  of  heat  expended  in  the 

industrial  cost  of  the  motor,  their  difference  is  ^-~  5°^*§  —  8.7  per  cent. 

9.465 

in  favor  of  the  engine  with  one  cylinder,  coming  to  the  point  of  the  prin- 
ciple which  I  stated  at  the  session  of  January  30, 1878,  concerning  jacketed 
engines,  viz.: 

That  it  is  always  possible  to  construct  a  vertical  beam  engine  with  one 
cylinder  and  four  valves,  consuming  saturated  steam  that  shall  be  at  least  as 
economical  as  the  "Woolf"  beam  engine. 

We  have  compared  the  two  experiments  which  are  alike  in  most  of  the 
transfers  of  heat,  etc.  There  are  also  others  which  should  conduct  us  to 
more  rigorous  conclusions.  Let  us  see,  meanwhile,  what  will  result  from 
the  whole  of  our  verified  experiments,  to  which  we  will  add  the  results 
upon  the  compound  of  the  French  Navy,  which  I  published  in  my  last 
memoir. 

Our  readers  may  perhaps  find  that  we  fall  into  fastidious  repetitions; 
but  the  figures  inscribed  in  Table  V.  shows  us  once  more  that  it  is  impos- 
sible to  draw  conclusions  if  one  is  not  in  possession  of  a  sufficient  series 
of  experimental  studies,  not  only  of  one  system  or  other,  but  even  from 
one  experiment  to  another  upon  the  same  engine.  What  is  the  use  of 
seeking  the  law  of  expansion,  of  substituting  a  curve  of  the  hyperbolic 
family,  of  comparing  adiabatic  curves  and  others  with  the  indicator  dia- 
gram, when  it  is  impossible  to  deduce  from  one  verified  experiment  the 
results  which  we  shall  obtain  when  we  impose  other  conditions  upon  the 
engine?  The  practical  theory,  the  verified  analysis  of  numerous  expert 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


281 


TABLE  V. 


Si, 

g- 

«« 

«* 

*' 

Is" 

ftS  * 

og- 

Pi 

M 

pansion. 

ii 

1 

ft 

o  » 

8§l  ||a' 
SlliJfJ 

3  ft  o  to  bOi 
"S    -^      2  . 

li 

2  s 
II 

|M 

»>°M 

ference 
iternal  h 
/o  -  Uj. 
ft  lories. 

>,«° 

•°Sft 

III 

"2 

H 

^*f-H   -2 

<v« 

&«w 

*-*  ^SJ   Q 

c  o"^ 

d 

M 

13 

0 

n      £~° 

ft 

ft 

ft 

DOUBLE  CYLINDERS. 

j 

I.  "Woolt"  vertical  jack-  ( 

143 

28 

6.731 

0.181 

18.6 

8.273 

83 

10.019    —25.88 

7.8 

eted    1 

215 

13 

6.878 

0.226 

15.6 

8.149 

86 

9.465      +1.24 

8.3 

II.  "  Woolt"  vertical  jack-  J 

185 

7 

7.384 

0.234 

24.1 

9.730 

78 

12.411    —31.89 

3.5 

eted    ..          1 

347 

7 

7.112 

0.293 

17.4 

8.614 

87 

9.864    —17.40       3.4 

III.  "Wooir   horizontal! 

130      6 

7.290    0.253 

20.1 

9.120 

86 

10.563      —3.63 

1.2 

jacketed              ....    1 

180      6 

7.328    0.295 

17.4 

8.878    89 

9.975      —6.12 

0.7 

Compound  vertical  jacket 

ed 

690 

5 

7.510 

0.216      13.4. 

8.671 

89 

9.975    +40.32 

5.7 

SINGLE  CYLINDERS. 

"Corliss"  horizontal  jack-  j 

105 

11 

7.188 

0.148 

10.0 

7.983    88 

9.071      —6.32!    12.0 

eted    1 

158 

6      7.307 

0.184 

8.1 

7.955    92 

8.640      —1.831      8.0 

Him    vertical    unjacketed, 

superheated  196°  

113      T 

6.655 

0.188 

9.7 

7.370    90      8.188      +1.66     12.5 

Hirn    vertical    unjacketed. 

superheated  231°  

154      4 

7.000 

0.215 

8.3 

7.633 

93      8.207    +12.37        7.8 

Hirn    vertical    unjacketed. 

j             | 

superheated  223°             1251    2 

7.8741  0.190 

8.9 

8.655 

91 

9.511     +20  52!     10.5 

Hirn    vertical    unjacketed, 

—  —  .    —  .  _ 

superheated  220°  

99      2 

7.763    0.178 

10.4 

8.063 

88      9.844    +16.82     14.1 

Hirn    vertical    unjacketed, 

saturated  steam  107 

7 

7.822 

0.213 

11.8 

8.837 

89 

9.929 

+5.12 

21.6 

Hirn   vertical    unjacketed, 

saturated  steam  

146 

4 

8.449    0.225 

9.7 

9.307 

92 

10.341 

—1.87 

15.4 

ments,  can  alone  give  us  the  solution  of  problems  to  which  they  still 
apply  formulae  which  are  only  experimental  in  name.  This  law  which  M. 
Hirn  has  stated,  and  which  my  preceding  memoirs  have  confirmed,  makes 
us  consider  the  formulae  called  experimental  of  expansion  and  work  as 
algebraic  distractions,  perhaps  interesting,  but  having,  from  a  practical 
point  of  view,  a  utility  hardly  worth  contesting. 

For  us  the  true  theory  of  the  steam  engine  created  by  M.  Hirn  com- 
pletes itself  every  day  that  new  experiments,  entirely  checked  and  ana- 
lyzed, are  made  public  and  added  to  those  which  we  have  published  after 
him. 

Have  I  not  compared  the  results  of  pure  experience  in  determining  the 
influence  of  the  vacuum,  of  throttling,  of  expansion,  of  the  addition  of  a 
separate  cylinder?  And  still  in  this  case  before  placing  the  principle  let 
us  leave  a  sufficient  margin  for  the  minor  irregularities  which  it  is  difficult 
to  avoid  practically. 

All  that  we  have  said  concerns  only  those  researches  which  are  en- 
titled "experimental  researches."  By  the  side  of  the  practical  theory  the 
generic  theory  of  the  employment  of  steam  as  an  intermediate  in  the  em- 
ployment of  force  retains  its  special  value.  The  fine  work  of  Zeuner,  for 
example,  conceived  in  the  purely  theoretic  manner,  remains  a  model 


282  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

of  the  method  to  be  followed  when  the  hypothesis  is  that  the 
surfaces  transmit  no  heat;  but  what  it  is  necessary  to  shun  with  the 
greatest  care  is  the  mixture  of  generic  theory  with  the  practical  theory 
of  which  the  starting  points  are  diametrically  opposed  one  to  the  other.. 

The  successive  analyses  have  already  given  all  the  remarable  peculiar- 
ities; in  each  of  the  experiments  we  have  used  them  to  determine  the 
influence  of  expansion  upon  the  transformations  of  the  steam.  We  shall 
also  ask  of  Table  \  a  collected  view  of  the  costs  and  the  circumstances 
which  influence  them. 

A  part  of  the  interesting  results  which  we  shall  note  concern  the  "Cor- 
liss,"  expansion  6,  and  the  horizontal  "Woolf"  with  the  same  expansion. 
They  present  the  relative  value  qf  single  and  double  cylinder  engines  in  a 
different  form  from  that  which  we  have  examined  when  we  consider  only 
the  parallelism  between  the  transformations  of  steam.  Thus,  with  the 
same  expansions  the  cost  of  a  total  H.  P.  corresponds,  7.307  k.  for  the 
"Corliss"  at  158  H.  P.,  and  7.290  and  7.328  k.  for  the  "Woolf"  with  130  and 
180  H.  P.  But  we  have  already  said  that  this  latter  had  an  insufficient 
compression  in  the  clearance;  if  this  compression  had  been  properly  regu- 
lated the  cost  would  descend  to  7  kilos,  of  steam  per  total  H.  P.  We 
should  then  find  an  intrinsic  difference  of  4  per  cent,  in  favor  of  expan- 
sion in  a  separate  cylinder,  a  difference  which  confirms  the  principle 
that  we  have  stated  concerning  the  generic  economy  of  this  kind  of 
engine. 

What  becomes  of  this  benefit  of  4  per  cent,  when  we  pass  from  the 
total  work  to  the  indicated  and  the  net  work;  that  is  to  say,  when  we 
occupy  ourselves  with  only  the  industrial  work  usefully  realized. 

The  negative  work  of  the  "Woolf"  engine  absorbs  20  per  cent,  at  130 
H.  P.  and  17  per  cent,  at  180  H.  P.,  while  the  "Corliss"  only  loses  8  per 
cent.,  which  brings  the  "Corliss"  6  per  cent,  ahead  of  the  "Woolf "under 
its  best  conditions  at  180  H.  P.  If  we  compare  the  cost  of  a  net  H.  P., 

valued  by  a  brake,  we  find  9'97^  ~  8'64~  =  13.5  per  cent.,  which  a  suffi- 

t/.y  /o 

cient  compression  will  reduce  4  per  cent.,  and  there  remains  a  practical 
gain  in  favor  of  the  "Corliss"  of  9.5  per  cent.,  working  at  the  same  expan- 
sions. 

We  see  that  the  cost  of  a  total  H.  P.,  7.307  k.  and  7.328,  are  equal  for 
the  "Corliss"  and  horizontal  "Woolf"  for  6  expansions,  158  and  180  H.  P. 
A  well-known  construction  would  give  the  same  vacuum,  0.184  k.,  to  the 
"Woolf"  as  the  "Corliss;"  but  the  negative  work  would  be  8  per  cent,  and 
11  per  cent,  at  least.  A  difference  of  3  per  cent,  should  be  added  for  fric- 
tion, being  92  and  89  per  cent,  respectively. 

The  total,  6  per  cent.,  could  be  reduced  by  4  per  cent,  by  proper 
cushion  and  there  remains  at  the  end  of  our  account  an  inferiority  of  2  per 
cent,  for  the  "Woolf"  working  at  the  same  expansion  as  the  single -cylinder 
"  Corliss. "  In  conditions  easily  realized  in  practice  the  consumption  of  the 
"Woolf"  per  net  H.  P.  would  be  8.8  k.  This  is  the  lowest  we  should  expect 
from  this  kind  of  engine.  In  my  preceding  paper  I  had  fixed  this  con- 


THE  ALSATIAN  EXPERIMENTS,  ETC. 


28.3 


sumption  at  9  k.  deduced  from  the  vertical  "Woolf "  and  the  "Him"  engine 
with  superheated  steam. 

With  different  expansions,  13  and  6,  but  with  equal  transformations  of 
steam,  the  costs  per  total  H.  P.  vary  5.9  percent,  against  the  "Corliss"  with 
the  same  vacuum  0.184  k.:  for  the  two  engines  the  back  pressure  work 
would  have  been  8  per  cent,  for  the  "Corliss"  and  13  per  cent,  for  the 
"Woolf,"  being  5  per  cent,  the  other  way;  there  remains  only  about  1  per 
cent,  advantage,  comparing  by  the  indicated  H.  P.  Industrially  this 
advantage  disappears  and  there  is  a  loss  of  5  per  cent,  against  the  "Woolf," 
the  friction  being  such  that  we  obtain  86  per  cent,  being  6  per  cent,  worse 
than  the  "Corliss"  at  92  per  cent,  mechanical  efficiency. 

We  have  then  the  right  to  conclude  that  the  single-cylinder  engine  is 
at  least  the  equal  of  the  double-cylinder,  although  to  this  day  with  different 
consumption  more  favor  is  shown  the  double-cylinder  engines. 

A  number  of  other  interesting  results  are  presented  by  our  table.  I  will 
point  out  those  given  by  superheating  without  going  into  details  on  the  sub- 
ject, the  question  having  been  many  times  treated  in  our  Bulletins,  then  the 
effect  of  throttling  reducing  from  347  to  185  H.  P.  For  the  other  experi- 
ments the  small  difference  in  generic  cost  is  the  other  way  and  may  be 
neglected. 

We  can  push  all  these  comparisons  very  far  into  the  most  intimate 
details  of  the  working  of  the  engine,  following  the  elementary 
method,  which  consists  simply  of  examining  all  the  results  of  our  verified 
experiments.  We  believe  that  we  are  rendering  a  service  to  our  readers  in 
leaving  to  each  the  particular  study  of  the  experiment  which  interests  him. 
Our  duty  should  be  to  point  out  the  path  to  be  followed;  to  give  a  sufficient 
number  of  verified  experiments  to  permit  the  engineer  to  find  the  points 
for  future  researches.  My  end  in  writing  this  paper  has  been  above  all  to 
confirm  by  a  sufficient  number  of  verified  analyses  the  principle  of  the 
equality  of  double  and  single  cylinder  engines  in  point  of  consumption,  to 
determine  the  degree  of  influence  of  a  more  or  less  prolonged  expansion, 
to  verify  again  the  influence  of  a  reduction  of  passageway  or  throttling  the 
steam  entering  the  cylinders. 


1 

X 

1 

1 

1 

!§ 

CONSUMPTION  OF  DRY  STEAM 

d 

o 

Pi 

l^ 

Cfl 

Pi 

Pi 

s5 

PER  HOUR  IN    DIFFERENT 

"3 

W  UJ 

|§ 

—  '  oj 

C43 

hi  °° 

&Pn 

ENGINES. 

§ 

13 

!i 

•e3 

11 

«! 

IB 

H 

EH 

,£] 

W 

^ 

u 

Woolf  engines  jacketed 

13 

6  8 

14 

7  9 

87 

9  8 

1.14 

7 

7.1 

13 

8  2 

88 

9.3 

1.16 

U                              M                                         M 

6 

7.3 

12 

1.3 

90 

9.2 

1.15 

Compound  engines,  jacketed.  .  . 

5 

7.5 

12 

8.5 

90 

9.5 

1.19 

Corliss,  jacketed  

6 

7.3 

8 

7.9 

92 

8.6 

1.08 

Him,  superheated 

7 

6.6 

9 

7.2 

90 

8.0 

1.00 

284  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

All  these  actions  we  have  seen  are  in  a  restricted  circle;  we  can  fix  for 
the  builders  the  lower  limit  of  consumption,  a  limit  which  we  should  seek  to 
attain  by  good  designs.  We  can  give  at  the  same  time  the  corresponding 
consumption  of  coal,  but  we  warn  the  reader  that  this  valuation  should 
never  be  taken  as  a  unit  of  comparison,  the  calorific  power  of  coal  being  as 
variable  as  their  localities.  We  will  admit,  however,  that  from  the  numer- 
ous experiments  made  by  the  Society  of  Mulhouse  upon  boilers,  a  weight 
of  dry  steam,  eight  times  the  weight  of  the  coal  can  be  produced  by 
medium  coal  (Kon champ).  This  is  the  figure  on  which  we  will  give  the  fuel 
required. 

The  consumptions  of  dry  steam  per  hour  for  indicated  and  net  horse  - 
power,  are  deduced  from  the  total  horse-power  found  experimentally 
They  have  a  real  base,  a  definite  point  of  departure  essentially  certain  in 
practice. 

The  back  pressure  work  varies  from  0.200  k.  to  0.220  k.  for  the  double- 
cylinder  engines  and  0.180  to  0.200  k.  for  single  cylinders,  values  which  it 
is  always  possible  to  secure  by  proper  arrangements  of  the  exhaust. 

Concerning  the  mechanical  efficiency,  three  of  them  have  been  ob- 
tained directly  by  brake.  The  others  have  been  deduced  from  these  same 
experiments  by  comparing  the  indicator  diagrams.  We  have  seen  that 
there  cannot  be  an  error  of  1  per  cent.  The  net  power  is  then  exact.  It 
is  that  which  represents  the  industrial  work. 

In  this  form,  which  only  differs  from  Table  V.  by  the  uniformity  of  the 
back  pressure  work,  we  perceive  clearly  the  influence  of  an  expansion  pro- 
longed from  7  to  13,  a  generic  gain  of  4  per  cent.,  which  industrially  is  2 
per  cent.  The  compound  engine  comes  after  the  "  Woolf." 

The  horizontal  "Woolf"  and  horizontal  "Corliss"  have  the  same  generic 
consumption  for  the  same  expansion.  This  disappears  and  the  "Corliss"  is 
6.5  per  cent,  better  than  the  "Woolf,"  industrially. 

Finally  the  steam  per  total  horse -power  for  the  "Woolf"  expanding  13 
times  is  within  3  per  cent,  of  the  Hirn  unjacketed  with  steam  heated  to 
200°  C.,  which  becomes  12  per  cent,  in  favor  of  the  superheating,  when  we 
compare  the  net  horse-power,  while  the  "Corliss"  is  only  7  per  cent  behind 
the  Hirn. 

In  presence  of  these  results  have  we  not  the  right  to  ask  what  dis- 
coveries have  been  made  since  the  day  that  Watt  created  the  engine? 

Without  speaking  of  the  well-balanced  mechanism  of  the  beam  engine 
we  can  say  that  this  man  of  genius  had  produced  the  heat  engine  complete 
in  its  three  parts;  the  separate  condenser,  the  steam  jacket,  an  expansion 
prolonged  as  useful,  leaving  to  those  who  came  after  to  seek  the  attain- 
ment of  high  pressures,  the  construction  of  boilers  at  his  time  prohibiting 
him  from  following  the  complete  realization  of  the  principles  of  expansion 
which  he  had  stated. 

Also  is  there  not  in  the  series  of  improvements  in  the  construction  of 
engines  that  we  have  been  studying,  a  marked  discovery  in  the  history  of 
the  heat  engine,  bringing  another  order  of  ideas,  born  nearly  at  the  same 
time  as  thermodynamics,  of  which  it  is  one  of  the  best  applications? 


THE  ALSA  TIAN  EXPERIMENTS,  ETC.  285 

Each  of  my  readers  has  always  understood  that  I  refer  to  the  discovery 
made  by  Hirn  and  stated  in  our  Bulletins  for  1855,  for  it  was  at  that  time 
that  he  demonstrated  the  thermic  influence  of  the  metallic  surface  of  the 
inside  of  the  cylinders  upon  the  inclosed  steam.  This  discovery,  analyzed, 
discussed  and  completed  by  twenty  years  of  continual  research  in  which 
he  has  kindly  associated  me,  has  conducted  him  to  a  method  of  analysis 
that  he  has  called  the  "Practical  Theory  of  the  Steam  Engine. "  We  have 
not  insisted  upon  the  exact  character  and  almost  elementary  simplicity 
which  is  one  of  the  remarkable  features  of  this  practical  theory.  As  to 
its  importance,  it  is,  I  think,  placed  beyond  doubt  by  the  value  of  the 
facts  that  it  has  permitted  us  to  define  in  the  course  of  this  paper. 


CHAPTER     VI. 

STEAM  HEATING.* 
INTRODUCTION. 

The  subject  of  Steam  Heating  will  be  presented  in  this  Chapter  under 
the  following  heads: 

A.— The  theory  of  steam  heating,  the  laws  of  the  transmission  of  heat 
and  the  coefficients  used  in  reducing  this  theory  to  practice. 

B. — A  description  of  the  various  systems  in  use  in  the  United  States, 
with  a  note  on  the  magnitude  of  the  works  employed  up  to  1881. 

C. — A  detailed  description  of  the  apparatus  used  and  the  experiments 
made  under  the  direction  of  the  writer. 

D. — The  project  of  heating  a  cotton  mill  with  steam,  and  a  comparison 
of  the  cost  when  condensing  and  non- condensing  engines  are  used  to  drive 
the  mill. 

A.— The  Theory  of  Steam  Heating. 

The  transfer  of  heat  takes  place  by  three  processes:  Radiation,  Con- 
duction, Convection. 

In  heating  a  room,  for  example,  with  an  open  grate  fire,  the  heat  in 
the  room  is  mostly  radiant  heat.  The  heat  of  the  fire  is  given  to  the  gas 
and  air  in  the  flue  and  is  carried  away  by  convection.  With  radiation  we 
have  little  to  do,  as  in  all  heating  apparatus  the  heat  is  brought  to  and 
delivered  from  some  intervening  solid  body  by  fluids  and  passed  through 
the  solid. 

The  rate  of  conduction  through  a  plate  is  expressed  by  a  well-known 
formula  (Eankine's  "Steam  Engine, "p.  260.) 

mf  m 

q—  where  T  and  F  are  the  temperatures  of  the  fluids  on 

a  +   a'    +   px 

either  side  of  the  plate,  a  and  a*  are  the  coefficients  of  conductivity  from 
the  fluids  to  the  plate,  and  x  the  thickness  of  the  plate,  p  the  conductivity 
of  the  plate  itself. 

For  British  units  with  x  in  inches  p  =  0.0043  heat  units  per  square  foot 
per  hour  for  iron  plates,  a  quantity  which,  with  ordinary  thicknesses,  is  so 
small  that  it  may  be  neglected  for  iron  plates. 

The  terms  <rand  a'  depend  entirely  upon  the  nature  of  the  surfaces  and 
upon  the  rapidity  with  which  the  fluids  are  circulated  and  the  heat  brought 
to  and  removed  from  the  plate  or  surfaces  in  question.  What  is  required 

*A  paper  read  before  the  Engineers'  Club  of  St.  Louis,  June,  1882,  by  the  Author. 


STEAM   HEATING.  287 


for  us  as  engineers  is  to  determine  the  limits  which  appear  in  practice, 
leaving  to  the  physicist  the  general  investigations  of  the  laws  of  the  sub- 
ject. 

It  has  been  suggested  (v.  Rankine's  "Steam  Engine,"  p.  260)  that  for 

_  irrv T}^ 

iron  plates  <r  +  </  may  be  put  equal  r_^—~,  and  then  q  =   -'  -'-  and 

a   =   ^  )2 ,  and  he  further  states  that  for  air  and  water  in  a  furnace 

q 
and  boiler  a  is  from  160  to  200  for  q  in  British  units. 

When  the  fluids  are  steam  and  air,  we  should  expect  from  the  greater 
mobility  of  steam  than  water,  a  greater  rate  of  conduction,  and  we  are  not 
disappointed. 

From  many  experiments  in  the  open  air,  the  steam  condensed  per 
square  foot  of  pipe  surface  of  |  inch  thick  wrought  iron  is  found  to  be  1| 
pounds  per  square  foot  per  hour  when  T'  =  220°  F.  and  T  =  20°  F. 

In  British  heat  units,  the  heat  given  up  per  pound  of  steam  is  969 
units;  but  as  the  water  temperature  is  not  given  and  is  usually  from  180°  F. 
to  200°  F.,  we  shall  make  no  large  error  by  taking  in  this  and  in  other  in- 
vestigations the  heat  delivered  by  condensing  1  pound  of  steam  as  1,000 
heat  units;  we  then  have. 

«  =  <JL~_r?  =  20°  x  20°  =  29  nearly. 
q  137o 

Experiments  made  by  the  writer,  which  will  be  described  hereafter, 
give  values  of  a  as  great  as  100.  As  experiments  were  made  under  the 
usual  usage,  and  are  more  nearly  in  accordance  with  practice,  the  results, 
moreover,  giving  for  the  larger  values  of  a  a  less  rapid  transmission  of 
heat,  they  are  obviously  the  safer  to  follow  in  designing  heating  surface. 
The  great  difference  is  to  be  attributed  entirely  to  difference  in  the  circu- 
lation of  the  air  by  which  the  condensation  was  effected. 

By  experiments  made  in  the  United  States  Navy,  seepage  63  of  "Trea- 
tise on  Boilers,"  by  Engineer-in- Chief  Wm.  H.  Shock,  the  transfer  of  heat 
is  stated  to  be  in  proportion  to  the  difference  in  temperature,  instead  of 
the  square  of  the  difference  as  taken  by  the  writer. 

The  experiments  there  given  appear  to  give  the  same  quantities  as 
those  noted  above  in  the  open  air,  but  would  be  reduced  to  q  =  2.6  (T'  —  T) 
by  the  writer's  experiments  under  the  practical  conditions  commonly 
found,  and  this  seems  to  agree  more  closely  with  the  usual  practice  in  the 
United  States,  and  we  shall  therefore  use  this  formula  in  preference  to  the 
other  and  more  scientific  one. 

The  heat  required  in  any  given  building  will  depend  upon  the  heat 
transmitted  to  the  external  air  around  the  building  and  the  amount  of  air 
carried  through  the  building  or  the  ventilation.  The  former  effect  is 

m'  rp 

measured  by  the  same  formula,  q  =    -  — ,  where  of  course  the  con- 

G    +    (7      +    pX 

stants  have  different  values,  and  the  latter,  by  the  quantity  of  air  used  in 
ventilation  and  the  amount  of  heat  given  to  the  air. 

The  constants  a,  af  and  p  vary  very  much  with  the  materials  of  the 


288  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 

walls  and  roofs,  and  the  kinds  of  surfaces;  but  the  most  important  cause 
of  variation  is  the  rapidity  with  ^vhich  the  heat  is  removed  from  the  out- 
side by  the  action  of  the  wind,  and  the  variation  found  here  is  so  great 
that  the  minor  changes  become  less  important.  The  effect  of  ventilation 
is  easily  computed  from  the  weight  and  specific  heat  of  air  when  the  quan- 
tities are  known. 

The  values  of  p  and  a  +  a'  are  given  by  some  writers  on  heating  and 
ventilation,  but  our  safest  course,  as  engineers,  will  be  to  seek  the  practi- 
cal limits  given  by  experience,  and  we  find  the  limits  pretty  wide. 

According  to  D.  K.  Clark  ("Manual  for  Mechanical  Engineers,"  p.  488), 
M.  Peclet  found  that  for  T'  —  T  =  36°  F.  each  square  foot  of  wall 
would  transmit  26  British  units  per  hour,  and  that  the  glass  windows 
passed  heat  at  the  rate  of  30  units  in  place  of  26.  The  same  author  gives, 
on  the  authority  of  Mr.  Hood  (Idem.,  p.  481),  the  rate  of  1.4  units  per 
square  foot  per  hour  per  degree  of  F.  of  Tf  —  T  for  glass  windows,  or  for 
36°  q  =  50.4  units,  and  the  further  statement  that  q  varies  with  the  square 
root  of  the  velocity  of  the  wind.  From  experiments  by  the  author  on  large 
buildings,  the  transmission  varied  from  0.67  to  1.25  units  per  square  foot 
per  hour  per  degree  F.  of  T'  —  Tfor  the  whole  surface  of  walls  and  win- 
dows. The  larger  values  were  produced  by  wind  action,  and  are  the  ones 
that  should  be  taken  in  practice.  The  effects  of  a  liberal  ventilation  are 
included  in  the  above  results.  The  experiments  will  be  given  later. 

Summing  up  these  results  we  find  that  the  transfer  of  heat  from  steam 
to  air  may  be  expressed  as  q  =  a  (T'  —  T)  where  T'  and  Tare  the  temper- 
atures of  the  steam  and  air  on  each  side  of  a  thin  iron  surface,  and  q  is  the 
rate  of  heat  units  per  unit  of  surface  per  hour. 

For  T'  and  T  in  degrees  F.  and  q  in  British  heat  units,  a  =  2.6  for  1 
square  foot  per  hour. 

For  Tf  and  T  in  degrees  centigrade  and  q  in  calories  per  square  metre 
per  hour,  a  =  12.48. 

For  the  external  surface  of  a  building,  including  walls,  windows  and 
roof  together,  and  taking  no  account  of  the  material  for  the  maximum 
transfer  of  heat,  q  =  c  (Tf  —  T). 

For  q  in  British  heat  units  per  square  foot  per  hour  c  =  1.25  for  F3. 

For  q  in  calories  per  square  metre  per  hour,  c  =  6  for  0°. 

For  the  surface  of  a  steam  boiler  as  ordinarily  constructed  ^  -^2 

a 

For  British  heat  units  and  F.  per  square  foot  per  hour,  a  =  200. 
For  French  heat  units  centigrade  degrees  and  meters,  per  square  meter 
per  hour  in  calories,  a  =  23.14. 

1  =  0.0432. 
a 

For  keeping  any  building  permanently  warm  we  must  have  a  steady 
flow  of  heat  from  the  furnace  to  the  boiler,  from  the  boiler  through  the 
heaters  to  the  air  in  the  building  and  from  the  walls  to  the  external  air. 
The  same  number  of  heat  units  per  hour  must  be  transferred  in  each  case, 
whence  it  becomes  easily  possible  to  find  the  heating  surface  and  boiler 


STEAM  HEATING. 


289 


surface  to  warm  any  given  building,  taking,  of  course,  the  most  unfavor- 
able cases,  and  allowing  for  losses  between  the  boilers  and  heaters,  and  for 
the  ventilation. 

Another  method  of  expressing  the  transfer  from  heaters  to  building  is 
by  the  number  of  units  of  volume  which  can  be  warmed  by  a  unit  of 
heating  surface,  and  this,  of  course,  varies  with  the  proportions  of  the 
building  and  the  range  of  external  temperature,  but  the  application  must 
be  to  buildings  of  ordinary  proportions,  and  though  more  commonly  used, 
is  really  less  reliable  in  its  results. 

With  the  practice  of  the  Dubuque  Steam  Supply  Company,  at  Dubuque, 
Iowa,  we  find  that  with  the  external  air  ranging  to  0°  F.  or  —  18°  C.,  1 
square  foot  of  heating  surface  warms  a  number  of  cubic  feet  as  follows,  in 
columns  2  and  4. 


WHEN  HEATEBS    ABE    IN 
SAME  ROOMS. 


Cubic  ft.  per 
sq.  ft. 

Cubic  metre 
per  square 
metre. 

Cubic  ft.  per 
sq.  foot. 

Cubic  metre 
per  square 
metre. 

Dwellings 

50 

15 

40 

12 

Stores  wholesale  • 

125 

37 

100 

30 

%"         retail           

100 

30 

80 

24 

Banks  ) 

Offices                                             V 

70 

21 

60 

18 

Drufj  stores        ) 

Drv  goods 

80 

24 

70 

21 

Hotels,  large 

125 

37 

100 

30 

Churches  

200 

60 

150 

45 

WHEN  HEATEBS    ABE  IN 
BASEMENTS  AND  WABM 


To  reduce  these  numbers  to  cubic  metres  warmed  per  square  metre 
we  multiply  by  0.3,  obtaining  columns  3  and  5. 

B.     Various  Systems  in  the  United  States. 

In  the  United  States  the  application  of  steam  for  heating  was  begun 
in  1842,  by  J.  J.  Walworth  and  Joseph  Nason,  and  the  first  building  heated 
by  steam  was  a  cotton  mill  in  Portsmouth,  N.  H.  The  exhaust  steam  from 
the  engine  was  used  very  successfully,  and  from  that  time  to  the  present 
there  has  been  a  steady  increase  in  the  number  and  magnitude  of  the 
works  constructed  for  this  purpose.  This  has  been  owing  to  the  severity 
of  the  climate  and  the  large  number  of  new  buildings  erected  in  the  rapid 
growth  of  the  country.  The  business  of  the  Walworth  Manufacturing 
Company,  of  Boston,  Mass.,  in  constructing  steam  heating  plant  is  now 
$1,500,000  per  annum,  and  there  is  in  the  United  States  a  business  estimated 
by  competent  authorities  at  $6,000,000  per  annum,  which  has  for  the  past 
30  years  averaged  $2,000,000  per  year.  In  other  words,  there  is  now  in- 
vested in  the  United  States  about  $60,000,000  in  steam  heating  apparatus, 


290  STEAM  USING;  OB,  STEAM  ENGINE  PRACTICE. 

so  that  in  this  subject  there  is  no  lack  of  precedents  for  many  kinds  of 
apparatus. 

There  are  two  classes  of  plant  used,  as  was  indicated  by  the-columns 
2  and  4  for  the  table  above. 

When  the  heaters  are  placed  in  the  rooms  to  be  heated,  the  heating  is 
said  to  be  direct.  When  the  heaters  are  used  to  warm  air  in  separate 
chambers,  which  air  is  then  transferred  through  flues  to  the  rooms  to  be 
warmed,  the  heating  is  called  indirect. 

The  choice  between  these  systems  is  to  be  governed  by  other  condi- 
tions. Where  the  air  is  not  renewed  frequently,  or  where  the  space  to  be 
warmed  is  large  in  plan  but  not  in  height,  the  direct  system  appears  pre- 
ferable; but  where  large  ventilation  is  required,  or  the  building  is  lofty, 
the  indirect  method  offers  many  advantages.  It  appears  necessary  to  pro- 
vide more  heating  surface  by  the  latter  method;  but  the  labor  and 
expense  of  fittings  is  often  much  reduced  thereby,  while  with  improved 
arrangements  there  is  little  difference  in  the  surface  required.  Usually 
the  movement  of  the  air  by  which  the  indirect  system  heats  a  building  is 
effected  by  gravity,  but  in  some  instances  fans  have  been  employed,  re- 
quiring, of  course,  power  to  drive  them. 

In  regard  to  the  different  forms  of  heaters  used  in  the  United  States 
there  is  great  variety,  from  the  single  line  of  large  pipe  and  the  manifold 
lines,  where  the  steam  flows  through  several  pipes  side  by  side,  to  the 
elegantly  finished  work  used  in  all  the  large  hotels,  and  the  complicated 
heaters  used  with  the  indirect  method. 

Within  the  last  three  years  preceding  1881  steam  heating  has  assumed 
a  new  form,  by  the  use  of  long  lines  of  pipes  underground,  thus  placing 
the  subject  upon  the  basis  of  a  gas  or  water  supply.  Companies  for  this 
purpose  have  been  formed  and  works  put  in  operation  in  many  places  in 
the  United  States.  The  table  opposite  gives  some  information  concern- 
ing these  works.  This  list  is  being  rapidly  extended,  and  after  passing 
its  experimental  stage  the  subject  can  be  placed  upon  a  good  financial 
basis.  At  the  present  time,  although  the  matter  is  a  success  from  the 
physical  standpoint,  yet  rates  and  charges  are  still  in  an  unsettled  con- 
dition, and  the  owners  by  no  means  satisfied  in  most  of  these  places. 

From  experiments  with  pipe  laid  and  protected,  as  such  companies 
protect  them,  a  loss  of  heat  of  the  pipes  is  found  at  50  British  heat  units 
per  square  foot  per  hour  with  steam  at  258°  F.,  the  ground  at  say  58°,  0.05 
pounds  per  square  foot  per  hour  being  the  condensed  water  by  weight. 
Experiments  by  the  writer  gave  the  same  value,  but  in  long  lines  a  further 
loss  takes  place  by  leakage  and  by  imperfect  traps,  a  very  essential  part 
of  the  system.  In  fact  the  experience  at  Dubuque  is  that  about  one-half 
of  the  steam  made  is  wasted,  according  to  the  statement  of  the  superin- 
tendent. 

Steam  for  heating  is  carried  at  all  pressures  in  the  United  States,  and 
while,  as  well  known,  no  economy  in  fuel  can  result  from  the  use  of  high 
pressures,  yet  a  smaller  plant  can  be  made  to  do  the  work,  and,  in  fact, 
the  first  remedy  in  cold  weather  for  cold  rooms  is  to  raise  the  steam  pres- 


STEAM  HEATING. 


291 


sure  until  the  increased  energy  of  transmission  of  the  heaters  produces 
the  desired  result. 


City  and  State. 
Lockport,  New  York 


Pipe  Underground. 
.3  miles. 
800  feet  6    inches 


Dubuque,  Iowa 

Auburn,  New  York 
Detroit,  Michigan 

Milwaukee,  Wisconsin. 


1,960 
3,818 
4,441 
205 
2,073 
2,508 
643 
1  mile 

5 
4 
3 
2 
Ifc       " 
154      " 
1 

et  6    inches 
8 
smaller  than  6  in 
'  10    inches 

>rk. 

1 

5,000  fe 

2,000 
5,000 
'    585 

"1 

I  2,540  "  8 

I  5,156  "  6 

<!     875  "  5 

|5,195  "  4 

1,300  "  3 

(.6,900  "  smaller  pipe. 


Remarks. 

Heats  3,500,000  cubic 
feet  space;  has  100 
consumers 

Boiler  capacity  25,000 
Ibs.  water  per  hour, 
from  40°  F.,  at  280°  F. 
evaporation. 

Heats  6,000,000  cub.  ft. 


Heats  5,000,000  cubic 
feet  and  runs  10  en- 
gines. 


Boilers  for  steam  heating  are  of  all  sorts  and  kinds,  and  the  only  point 
which  is  vital  in  designing  them  is  to  keep  in  mind  the  range  of  action  to 
which  they  will  be  subjected.  For  the  work  of  a  boiler  in  making  steam 
for  heating  is  more  like  that  of  a  locomotive  boiler  than  anything  else. 
Every  degree  change  of  temperature,  and  every  change  in  the  wind  is  felt 
by  the  men  with  the  shovels,  and  quickness  of  steaming  and  capacity  of 
furnace  for  burning  fuel  is  essential.  Grate  surface  enough  must  be  pro- 
vided to  do  the  wrork  in  the  coldest  weather;  and  this  grate  will  be  too 
large  for  economic  evaporation  in  milder  weather;  and  while  large  boiler 
surface  is  a  good  thing  it  is  not  judicious  to  invest  in  a  boiler  large  enough 
to  work  at  a  high  economy  of  evaporation  during  a  few  days  only  in  a  year 
of  the  hardest  work.  It  is  more  economical  to  crowd  the  boilers  at  the  ex- 
pense of  the  fuel  at  such  times,  and  a  boiler  must  be  provided  which  can 
be  crowded  hard. 


C.—  Apparatus  and  Experiments  Made  by  the  Author. 

In  the  winter  of  1878  the  writer  placed  before  the  directors  of 
Washington  University  in  the  City  of  St.  Louis,  Missouri,  a  plan  for  heat- 
ing a  portion  of  the  buildings  belonging  to  the  University  by  steam, 
which  plan  was  adopted  by  them  and  built. 

The  central  group  of  buildings  consists  of  the  Academy,  the  Museum 
of  Fine  Arts,  the  Manual  Training  School,  the  University,  Laboratory,  and 
Gymnasium;  the  three  latter  are  called  collectively  the  University.  To 
the  west  is  the  Mary  Institute,  with  its  own  boiler,  and  to  the  east  the  Law 
School,  occupying  the  old  building  erected  for  the  Mary  Institute;  the 
future  of  this  building  being  uncertain,  it  has  not  been  connected  for 
steamheating.  The  Mary  Institute  heating  apparatus  is  mainly  indirect, 


292  STEAM  USING;   OR,  STEAM  ENGINE  PRACTICE. 


and  consists  of  beaters  hung  in  the  basement  in  small  air  chambers  con- 
nected by  flues  to  the  different  rooms.  The  air  heated  is  taken  either  from 
the  basement  or  from  out-doors  as  desired.  The  operation  is  quite  satis- 
factory; the  steam  is  at  present  supplied  by  two  boilers  in  the  building, 
but  it  is  probable  that  it  will  be  connected  to  the  central  group  and  oper- 
ated from  the  main  boiler  house  in  a  short  time.  It  has  now  been  in  use 
for  four  years.  The  condensed  water  returns  directly  to  the  boilers. 
The  heaters  of  cast-iron  are  corrugated  castings  short  and  placed  hori- 
zontally. 

The  Academy  and  Museum  of  Fine  Arts  are  heated  by  fittings  put  in 
by  the  Walworth  Manufacturing  Company.  In  the  Academy  cold  air  is 
taken  through  openings  in  the  walls  close  to  the  heaters,  and  the  foul  air 
passes  through  flues  from  the  rooms  to  the  top  of  the  building  and 
escapes.  The  steam  and  return  mains  are  led  around  the  basement,  and 
vertical  steam  and  return  pipes  rise  through  the  buildings  with  one  heater 
connected  to  them  on  each  floor.  As  little  horizontal  pipe  is  used  as  pos- 
sible, and  that  is  kept  in  the  basement.  The  steam  pipes  rise  all  the  way 
and  the  return  pipes  fall  all  the  way.  The  horizontal  steam  main  must 
be  kept  dry  and  the  return  main  full  of  water  in  order  to  prevent 
what  is  known  as  "snapping"  a  phenomenon  sure  to  attract  attention 
when  it  does  occur,  and  which  is  sometimes  dangerous  to  the  joints  of 
the  pipes. 

"Snapping"  is  caused  in  this  way:  when  any  of  the  condensed  water 
finds  its  way  into  steam  that  is  warmer  than  itself,  it  causes  a  sudden  con- 
densation, and  the  steam  closes  up  so  rapidly  that  a  shock  and  violent 
sound  result.  With  large  pipes  and  well-defined  currents  of  steam  the 
water  condensed  remains  at  the  temperature  of  the  steam  and  is  swept 
along  with  it.  To  illustrate  more  fully,  if,  in  the  Academy  building,  a 
heater  on  the  upper  floor  is  shut  off,  steam  will  condense  in  the  upper 
portion  of  the  vertical  stand-pipe,  and  there  being  no  current  in  the  upper 
portion  and  not  much  below,  the  water  stands  in  drops  on  the  iron  cool- 
ing and  accumulating  till  it  falls  into  the  hotter  steam  below.  A  sound 
like  the  crack  of  a  rifle  is  the  result.  The  remedy  is  to  open  the  heater 
on  the  summit  of  this  pair  of  pipes,  or  to  connect  the  stand-pipes  them- 
selves; a  better  but  more  expensive  way  is  to  put  in  a  pair  of  vertical  pipes 
for  each  heater  from  the  mains  in  the  basement,  with  the  valves  at  the 
bottom.  The  greater  portion  of  the  University  buildings  is  heated  by 
tubular  heaters  in  the  basement,  the  warm  air  being  led  to  the  various 
rooms  by  flues  in  the  walls  and  moved  only  by  gravity.  The  old  heaters 
were  of  cast-iron  heated  by  fires  made  in  them,  and  the  new  heaters  were 
applied  to  the  same  system  of  flues.  The  heaters  were  described  in  a 
paper  by  Mr.  Chas.  F.  White  before  the  Club,  and  printed  in  The  American 
Engineer.  Certain  rooms  in  the  upper  floors  are  unprovided  with  wall 
flues  and  are  warmed  by  direct  heaters;  as  these  heaters  are  connected  to 
a  pair  of  horizontal  pipes  of  considerable  length,  the  condensed  water  does 
not  drain  properly.  The  drying  tables  and  sand  baths  in  the  chemical 
and  physical  laboratories  and  one  small  heater  is  placed  in  a  small  room 


STEAM  HEATING. 


293 


on  the  first  floor  of  the  south  wing,  and  one  on  the  upper  or  second  floor 
of  the  Laboratory  building.  The  Gymnasium  is  to  have  heaters  of  the 
kind  in  the  upper  floor,  with  horizontal  mains  in  the  basement.  At  the 
west  end  of  the  University  building,  the  heating  surface  is  not  sufficient 
to  make  up  the  loss  from  the  walls,  and  the  upper  floors  draw  off  the  heat 
from  the  lower  rooms.  This  could  be  prevented  by  controlling  the  area  of 
the  flues  which  carry  away  the  warm  air,  but  will  be  remedied  by  placing 
heaters  in  the  lower  room.  With  the  exception  of  two  rooms  the  heating 
is  ample  in  the  coldest  weather. 

The  Manual  Training  School  is  heated  in  part  by  direct  and  in  part  by 
indirect  radiation.  The  two  lower  floors  with  the  four  workshops  are 
warmed  by  4  lines  of  2 -inch  pipe  along  the  foot  of  the  walls  under  the 
benches,  and  the  upper  or  school-room  floor  by  a  pair  of  tubular  heaters  in 
the  basement,  and  one  room  has  two  lines  of  pipes  on  three  sides.  The 
steam  is  taken  either  from  the  steam  main  or  from  the  exhaust  steam  of  the 
n  on -condensing  engine  used  for  running  the  tools  in  the  workshops.  The 
air  from  the  heaters  in  the  basement  is  conveyed  to  the  upper  floor  by  metal 
flues  passing  through  the  floors. 

The  dimensions  of  the  buildings  and  surfaces  met  with  are  given 
for  the  central  group  in  the  following  table  with  French  and  English 
units: 


APPROXIMATE  DIMENSIONS  OF  BUILDINGS  IN  THE  CENTBAL  GBOUP. 


Academy. 

Manual 
Training 
School. 

Museum 
of 
Fine  Arts. 

Gym- 
nasium 

Uni- 
versity. 

Volume,  c.  f  

450,000 

225,000 

500,000 

100,000 

750,000 

Volume,  c.  m  

12,600 

6,300 

14,000 

2,800 

21,000 

External  surface  in  sq.  ft.  .. 
External  surface  in  metres. 
Heating  surface  in  sq.  ft  
Heating  surface  in  metres.  . 
Volume  c.  f  .  to  1  sq.  ft.  heat 
ing  surface. 

36,000 
3,348 
3,500 
323 

129 

20,000 
2,418 
1,870 
174 

120 

36,000 
3,348 
3,300 
307 

152 

13,000 
1,200 
500 
46 

200 

80,000 
7,440 
6,000 
558 

125 

To  1  sq.  ft.  of  wall  

12  8 

11.2 

13  9 

7  7 

9  4 

Cubic  metres  to  1  sq.  metre 
heating  surface           

30 

36 

45 

60 

38 

To  1  sq  metre  wall  

3.8 

3.3 

4.2 

2.3 

2.8 

External  surface  to  heating 

10  3 

10.7 

10.9 

26. 

13.3 

The  boilers  are  three  in  number,  set  independently,  two  being  used  at 
once.  They  have  each  768  square  feet  of  heating  surface,  and  24  square 
feet  of  grate.  The  stack  is  12.25  square  feet  aperture  at  the  top,  and  is  105 
feet  above  the  grate  bars. 

All  fuel  is  weighed,  and  all  water,  fresh  or  return,  is  measured  either 
by  metre  or  weight  as  desired.  The  coal  used  is  bituminous,  from  the 
neighboring  mines  in  Illinois,  and  has  a  chemical  composition  capable  of 


294  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


evaporating  12  units  of  water  by  1  unit  of  coal  by  weight,  from  and  at 
212°  F.;  ash,  12  per  cent. 

Experiments  of  March,  1880.  Fuel  and  water  weighed  for  one  week; 
one  boiler;  maximum  coal  per  square  foot  of  grate,  38  pounds;  mean  eva- 
poration from  and  at  212°  F.,  6.49  pounds;  priming,  2  per  cent. 

Experiments  of  October,  1880.  Coal  weighed  and  water  by  meter 
(Worthington)  for  one  week;  two  boilers;  mean  evaporation  for  the  week, 
7.1  pounds;  maximum  for  24  hours,  7.9  pounds. 

As  the  meter  was  a  piston  meter,  the  results  are  not  likely  to  be  in  ex- 
cess of  the  truth  on  that  account.  The  weight  was  charged  each  time,  full 
and  empty  barrel  of  water,  and  the  time  noted. 

The  priming  by  the  method  of  Hirn.  The  work  done  was  exceedingly 
varied  in  the  March  experiments;  it  was  found  that  at  that  time  the  work 
from  6  A.  M.  to  12  noon  was  double  that  done  in  the  other  18  hours. 

Experiments  upon  the  transmission  of  heat  have  been  made  upon  the 
Academy  and  University  buildings  only,  the  quantity  of  water  condensed 
being  noted,  with  the  steam  pressure,  the  temperature  of  the  external  air, 
the  air  in  the  buildings  and  of  the  return  water. 

With  external  temperatures  from  10°  F.  to  45°  F.,  and  the  buildings 
from  60°  F.  to  75°  F.}  steam  from  260°  F.  to  280°  F.,  the  values  already  given 
for  a  were  found.  The  duration  of  the  experiments  was  from  three 
to  eight  hours,  taken  during  the  ordinary  operation  of  the  works.  The 
return  water  was  usually  from  190°  F.  to  210°  F.  The  experiment  for 
underground  condensation  was  made  in  the  same  way,  and  lasted  five 
hours.* 

The  construction  of  the  boilers  was  shown  in  the  paper  by  Mr.  "White 
above  referred  to. 

There  is  one  element,  not  yet  mentioned,  and  that  is  the  time  in  which 
the  buildings  must  be  warmed.  In  the  experience  of  the  writer  at  the 
University  buildings  the  Academy  can  be  warmed  in  cold  weather  in  three 
hours,  and  in  fact  the  steam  is  only  supplied  for  twelve  hours  out  of  the 
twenty- four.  The  University  building  with  the  indirect  heaters  has  to 
be  kept  warm  all  the  time,  and  in  cold  weather  takes  ten  or  twelve  hours 
to  get  warm  throughout.  For  rapid  heating,  the  direct  system  with  ample 
surface  appears  best  adapted;  but  for  steady  heating,  with  purity  of  air, 
the  indirect  is  to  be  preferred. 


D.    Designing  a  System. 


Suppose  that  it  is  required  to  design  the  heating  apparatus  for  a 
large  building.  This  will  include  the  boilers,  the  heaters  and  their  dis- 
position, and  the  choice  of  a  system  direct  or  indirect,  and  the  use  of  ex- 
haust steam  from  an  engine. 

*In  the  experiments  with  the  buildings  the  ample  ventilation  was  not  interfered 
with.  The  other  buildings  have  just  been  completed,  and  the  experiments  made  w}th. 
them  are  only  preliminary. 


STEAM  HEATIXi*.  295 


To  fix  our  ideas  let  us  consider  the  case  to  be  that  of  a  cotton  mill  with 
the  following  dimensions: 

In  English  measure,  328  feet  long,  40  wide  and  three  stories  of  13  feet 
in  height,  making  40  feet  say  as  the  height,  rectangular  in  plan,  having 
a  volume  of  52-1,800  cubic  feet  and  a  surface  of  42,560  square  feet. 

In  French  measure,  100  metres  long,  12  metres  wide  and  12  metres 
high,  having  a  volume  of  14,400  cubic  metres  and  a  surface  of  3,888  square 
metres. 

Such  a  mill  will  contain  10,500  spindles,  225  looms  and  the  proper  pro- 
portions of  cards,  with  the  other  machinery  belonging  to  the  manufacture 
of  cotton. 

Let  the  lowest  external  temperature  be  assumed  at  5°  F.  =  —  15°.  C., 
and  let  the  minimum  internal  temperature  be  assumed  at  59°  F.  =  15  C., 
values  which  would  be  likely  to  suit  most  localities  in  the  United  States, 
and  even  if  exceeded  would  not  be  very  often  passed.  The  range  of  wall 
transmission  will  then  be  from  59°  to  5°  =  54°  F.  =  30°  C.,  and  the  quan- 
tity of  heat  transferred  may  reach  54  x  1.25  units  per  square  foot  per  hour 
or  30  x  6.0  calories  per  square  metre  per  hour — 67.5  English  or  180  French 
units. 

67.5  x  42,560  =  2,872,800  heat  units  per  hour,  or 
180  x  3,888  =  699,840  calories  per  hour. 

To  decide  upon  the  amount  of  heating  surface  the  temperature  of  the 
steam  must  be  known.  The  choice  of  the  direct  or  indirect  methods  will 
probably  be  made  from  the  form  of  the  building,  which  covers  a  large  area 
and  is  not  very  high,  and  the  magnitude  of  the  rooms,  supposed  to  be  not 
more  than  two  to  a  floor,  as  direct  surface;  and-  the  kind  of  heaters  by 
economy  only,  to  be  pipes  laid  along  the  foot  of  the  walls,  or  rather  along 
the  walls  near  the  floors. 

The  temperature  of  the  steam  will  much  depend  upon  where  it  comes 
from,  from  a  separate  boiler  or  from  the  exhaust  of  an  engine,  and  we  will 
examine  three  cases: 

1.  A  separate  boiler. 

2.  A  non-condensing  engine. 

3.  A  condensing  engine. 

With  a  separate  boiler  we  are  not  limited  as  to  pressure  except  by  con- 
venience, and  we  will  assume  50  pounds  per  square  inch  above  the  at- 
mosphere, 65  pounds  absolute,  or  4J  atmospheres,  the  temperature  of 
the  steam  being  297°  F.,  or  148°  C.  297°  —  59°  =  238°  F.  =  T  —  T  = 

148°  _  15°   =  133°  C.,  q=(T'~~T^  =  566.44  heat  units  per  square  foot  per 

hour  =  1,528  calories  per  square  metre  per  hour. 

The  slight  difference  in  these  results  is  due  to  a  neglect  of  decimals  and 
is  of  no  practical  value. 

The  boiler,  to  give  this  amount  of  heat,  will  have  to  evaporate  2,873 
pounds  of  water  per  hour,  or  say  3,000  pounds,  and  will  require,  at  4 
pounds  of  water  evaporated  per  1  square  foot  per  hour,  an  amount  of  heat- 


296  STEAM  USING;  OR,  STEAM  ENGINE  PRACTICE. 


ing  surface  =  750  square  feet.  As  this  is  the  maximum  capacity,  we  find 
that  24  square  feet  of  grate,  with  coal  evaporating  6  pounds  of  water 
per  1  pound  coal,  burning  500  pounds  per  hour,  or  about  22  pounds  coal 
per  square  foot  of  grate,  is  an  ample  provision.  A  smaller  grate,  with 
careful  firing,  would  give  better  results  for  fuel,  but  would  not  be  as  easy 
to  work  on  cold  days. 

The  cost  of  such  a  boiler  set  in  the  United  States  would  not  be  far 
from  $1,300,  including  everything  ready  to  une,  but  not  counting  any  out- 
lay for  buildings  to  put  it  in.  The  cost  of  the  pipe  in  place  to  make  4,460 
square  feet  of  surface  for  1-inch  or  2-inch  pipe  would  be  about  40  cents  per 
square  foot,  or  $1,856.  Total  cost,  $1,856  +  $1,300  =  $3,156,  and  including 
contingencies,  say  $3,200  at  5  francs  per  dollar,  16,000  francs,  of  which  the 
boiler  cost  6,500  and  the  pipes  9,100  francs. 

Suppose  the  steam  had  been  at  212°  F.  or  100°  C.,  212°— 59°  =  153°  F., 
in  place  of  238°  for  T'  —  T,  but  the  transmission  is  now  reduced,  and  the 
surface  must  now  be  increased  1.55  times  to  7,192  square  feet,  say  7,200  or 
to  a  cost  of  13,950  francs;  total,  say  31,000  francs.  The  steam  temperature 
is  now  at  the  lowest  possible  in  a  non- condensing  steam  engine;  and  if 
such  an  engine,  using  2,800  pounds  of  steam  per  hour,  be  at  hand,  the  only 
outlay  involved  is  the  pipe  surface  of  14,000  francs,  say;  but  with  the 
more  active  circulation  of  the  steam  there  will  be  found  an  increase  in  the 
radiating  effect,  which,  however,  we  will  not  consider  here. 

We  have  then  a  decrease  in  the  cost  of  the  plant  of  400  dollars,  or  2,000 
francs,  which  is  equivalent  to  say  40  dollars  or  200  francs  per  year  interest 
and  repairs,  and  we  should,  of  course,  recommend  the  use  of  exhaust  steam. 

There  remains  to  be  considered  the  use  of  a  condensing  engine,  with  the 
exhaust  steam  at  say  100°  F.  =  38°  C. 

It  would  be  possible,  by  the  use  of  a  very  large  amount  of  pipe  surface 
and  a  very  carefully  arranged  drainage,  to  return  to  the  air  pump;  but  the 
great  cost  of  pipe  surface  and  the  practical  troubles  of  making  pipe  joints 
hold  in  vacuum  would  cause  us  to  reject  this  idea  as  impracticable,  and  there 
remains  the  use  of  a  separate  boiler,  or  the  running  of  our  condensing 
engine  as  a  non -condensing  engine  during  the  winter  months. 

For  ordinary  condensing  engines  the  increase  of  fuel  would  be  in  pro- 
portion to  the  increase  of  work  on  the  forward  stroke,  rendered  necessary 
by  the  increase  of  back  pressure,  and  in  such  cases  it  would  be  desirable 
to  use  a  separate  boiler,  as  the  fuel  used  would  be  great;  for  example,  the 
engine  using  400  I.  H.  P.,  with  4  pounds  of  coal  per  H.  P.  per  hour,  or  1,600 
pounds  of  coal  per  hour.  The  increase  of  fuel  may  be  measured  by  the 
increase  of  forward  work,  which,  of  course,  depends  upon  the  engine  used; 
but  if  the  forward  mean  pressure  had  been  30  pounds  and  the  mean  back 
pressure  3  pounds  per  square  inch  when  running  condensing,  the  forward 
pressure  will  now  be  raised  to  43  pounds,  and  the  back  pressure  to  16 
pounds,  the  fuel  from  1,600  to  2,292  pounds,  or  say  700  pounds  per  hour 
increase,  between  three  and  four  francs  per  hour,  say  40  francs  per  day  for 
the  maximum  work  in  heating,  but  this  must  be  kept  up  for  100  days,  or  a 
cost  per  year  of  4,000  francs. 


STEAM  HEATING.  297 


When  we  compare  this  with  our  separate  boiler  we  have  an  excess  of 
2,000  francs  to  begin  with,  but  also  the  cost  of  the  fuel  in  addition,  which 
cannot  be  taken  less  than  1,800  per  year,  as  estimated  below,  making 
together,  say  2,000  francs,  and  we  should  in  this  case  use  the  separate  boiler 
and  engine. 

When,  however,  we  have  the  mill  in  good  order,  and  have  the  best 
engine  in  use,  that  of  M.  Hirn,  using  superheated  steam,  we  find  that 
the  power  is  not  over  250  horse-power  and  the  fuel  2  pounds  per  hour 
per  I.  H.  P.,  or  500  pounds  per  hour  in  place  of  1,600,  the  increase 
500f*  _  500  =  217  pounds,  which  costs  about  one  franc  per  hour,  or  say 
$200  to  $230,  or  1,000  to  1,200  francs  per  year,  on  the  above  basis  of  100 
days  of  12  hours. 

The  cost  of  the  fuel  alone  for  the  separate  boiler  on  the  basis  given 
above  of  a  maximum  of  500  pounds,  and  say  an  average  of  300  pounds  of 
coal  per  hour,  would  be  from  30  to  40  cents,  or  1-fc  to  2  francs,  say  for  the 
100  days  of  12  hours;  $360,  or  1,800  francs,  as  estimated  above,  which,  with 
the  cost  of  the  boiler,  would  leave  us  $160,  or  800  francs  per  year  in  favor 
of  this  plan. 

We  find  then  that  with  non- condensing  engines  and  the  best  class  of 
condensing  engines,  the  use  of  exhaust  steam  is  desirable,  while  with  ordi- 
nary condensing  engines  a  separate  boiler  is  to  be  preferred. 

The  pipe  surface  for  7,200  square  feet  can  be  arranged  to  take  the 
exhaust  steam  from  the  engine  through  an  8-inch  or  the  10-inch  exhaust 
pipe  to  the  top  of  the  building,  and  to  open  into  2-inch  pipes  on  each  floor, 
in  two  directions,  uniting  in  a  descending  10-inch  pipe  carried  to  a  hot 
water  tank,  and  the  exhaust  to  be  either  circulated  or  turned  loose  into  the 
air  without  going  through  the  building. 

Seventy,  two  hundred  feet  would  require  14,400  feet  of  two-inch  pipe 
and  as  we  can  easily  place  300  feet  in  one  line  and  600  feet  in  the  two  lines, 
we  have  twenty  four  lines,  or  four  lines  of  2-inch  pipe  on  each  of  the  two 
main  walls.  The  end  walls  and  vertical  pipes  will  make  up  the  amount. 
Twenty-four  lines  of  2-inch  pipe  will  present  the  same  resistance  that  one 
line  of  10-inch,  and  we  need  fear  no  great  increase  of  back  pressure  above 
that  assumed.  (Two-inch  pipe  is  0.05  m.  diameter.)  The  wall  pipes  should 
fall  uniformly  1  in  200.  Each  line  of  pipe  should  have  its  own  valve  con- 
nections,  and  when  most  of  them  are  closed  the  steam  allowed  to  flow 
directly  into  the  air,  as  well  as  through  the  building,  to  avoid  back  pres- 
sure. One  and  one- quarter  inch  pipe  is  usually  preferred  to  larger  sizes,  as 
being  easier  to  bend  without  fracture. 

In  the  above  recommendation  of  the  use  of  exhaust  steam  by  discard- 
ing the  condenser  of  an  engine,  it  is,  of  course,  supposed  that  both  boilers 
and  engine  can  do  the  required  work  under  the  new  conditions  with  entire 
safety  and  satisfactorily.  This  can  only  be  ascertained  in  the  particular 
instance  by  a  careful  and  complete  examination  of  the  conditions  under 
which  the  engines  are  now  working,  and  the  change  should  not  be  made 
until  the  result  is  clearly  foreseen,  for  the  example  supposed  the  best  state  of 
things,  and  for  all  but  the  best  kind  of  condensing  engines  and  mills  in  the 


298 


STEAM  USING;  OR,  STEAM  ENGIXE  PRACTICE. 


best  order,  we  shall  not  find  it  advantageous  to  make  so  novel  a  departure, 
and  shall  use  the  separate  engine  and  boiler. 

To  get  the  pipe  surface  three  lines  of  2  inch  pipe  in  each  floor  may 
then  be  employed. 

In  the  United  States  the  cost  of  a  given  surface  of  pipe  is  about  the 
same  for  1-inch  and  2-inch  pipe,  the  labor  making  up  the  cost  to  the  same 
amount.  With  the  larger  sizes  the  cost  increases,  but  for  the  use  of  exhaust 
steam  the  larger  pipe  is  to  be  preferred,  unless  more  than  one  line  be  used 
at  once  in  the  example  above. 

[NOTE. — The  conclusions  of  the  above  paper  have  been  borne  out  by  the 
experience  of  the  winters  1880-81  and  1881-82.— C.  A.  SMITH.] 


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